Merge Walter's work on ipipe bugfixes.

IPython/Extensions/ipipe.py

@@ -1,2322 +1,2327 b''
 # -*- coding: iso-8859-1 -*-
 
 """
 ``ipipe`` provides classes to be used in an interactive Python session. Doing a
 ``from ipipe import *`` is the preferred way to do this. The name of all
 objects imported this way starts with ``i`` to minimize collisions.
 
 ``ipipe`` supports "pipeline expressions", which is something resembling Unix
 pipes. An example is::
 
     >>> ienv | isort("key.lower()")
 
 This gives a listing of all environment variables sorted by name.
 
 
 There are three types of objects in a pipeline expression:
 
 * ``Table``s: These objects produce items. Examples are ``ils`` (listing the
   current directory, ``ienv`` (listing environment variables), ``ipwd`` (listing
   user accounts) and ``igrp`` (listing user groups). A ``Table`` must be the
   first object in a pipe expression.
 
 * ``Pipe``s: These objects sit in the middle of a pipe expression. They
   transform the input in some way (e.g. filtering or sorting it). Examples are:
   ``ifilter`` (which filters the input pipe), ``isort`` (which sorts the input
   pipe) and ``ieval`` (which evaluates a function or expression for each object
   in the input pipe).
 
 * ``Display``s: These objects can be put as the last object in a pipeline
   expression. There are responsible for displaying the result of the pipeline
   expression. If a pipeline expression doesn't end in a display object a default
   display objects will be used. One example is ``ibrowse`` which is a ``curses``
   based browser.
 
 
 Adding support for pipeline expressions to your own objects can be done through
 three extensions points (all of them optional):
 
 * An object that will be displayed as a row by a ``Display`` object should
   implement the method ``__xattrs__(self, mode)`` method or register an
   implementation of the generic function ``xattrs``. For more info see ``xattrs``.
 
 * When an object ``foo`` is displayed by a ``Display`` object, the generic
   function ``xrepr`` is used.
 
 * Objects that can be iterated by ``Pipe``s must iterable. For special cases,
   where iteration for display is different than the normal iteration a special
   implementation can be registered with the generic function ``xiter``. This
   makes it possible to use dictionaries and modules in pipeline expressions,
   for example::
 
       >>> import sys
       >>> sys | ifilter("isinstance(value, int)") | idump
       key        |value
       api_version|      1012
       dllhandle  | 503316480
       hexversion |  33817328
       maxint     |2147483647
       maxunicode |     65535
       >>> sys.modules | ifilter("_.value is not None") | isort("_.key.lower()")
       ...
 
   Note: The expression strings passed to ``ifilter()`` and ``isort()`` can
   refer to the object to be filtered or sorted via the variable ``_`` and to any
   of the attributes of the object, i.e.::
 
       >>> sys.modules | ifilter("_.value is not None") | isort("_.key.lower()")
 
   does the same as::
 
       >>> sys.modules | ifilter("value is not None") | isort("key.lower()")
 
   In addition to expression strings, it's possible to pass callables (taking
   the object as an argument) to ``ifilter()``, ``isort()`` and ``ieval()``::
 
       >>> sys | ifilter(lambda _:isinstance(_.value, int)) \
       ...     | ieval(lambda _: (_.key, hex(_.value))) | idump
       0          |1
       api_version|0x3f4
       dllhandle  |0x1e000000
       hexversion |0x20402f0
       maxint     |0x7fffffff
       maxunicode |0xffff
 """
 
 skip_doctest = True  # ignore top-level docstring as a doctest.
 
 import sys, os, os.path, stat, glob, new, csv, datetime, types
 import itertools, mimetypes, StringIO
 
 try: # Python 2.3 compatibility
     import collections
 except ImportError:
     deque = list
 else:
     deque = collections.deque
 
 try: # Python 2.3 compatibility
     set
 except NameError:
     import sets
     set = sets.Set
 
 try: # Python 2.3 compatibility
     sorted
 except NameError:
     def sorted(iterator, key=None, reverse=False):
         items = list(iterator)
         if key is not None:
             items.sort(lambda i1, i2: cmp(key(i1), key(i2)))
         else:
             items.sort()
         if reverse:
             items.reverse()
         return items
 
+try: # Python 2.4 compatibility
+    GeneratorExit
+except NameError:
+    GeneratorExit = SystemExit
+
 try:
     import pwd
 except ImportError:
     pwd = None
 
 try:
     import grp
 except ImportError:
     grp = None
 
 from IPython.external import simplegeneric
 from IPython.external import path
 
 try:
     from IPython import genutils, generics
 except ImportError:
     genutils = None
     generics = None
 
 from IPython import ipapi
 
 
 __all__ = [
     "ifile", "ils", "iglob", "iwalk", "ipwdentry", "ipwd", "igrpentry", "igrp",
     "icsv", "ix", "ichain", "isort", "ifilter", "ieval", "ienum",
     "ienv", "ihist", "ialias", "icap", "idump", "iless"
 ]
 
 
 os.stat_float_times(True) # enable microseconds
 
 
 class AttrNamespace(object):
     """
     Helper class that is used for providing a namespace for evaluating
     expressions containing attribute names of an object.
     """
     def __init__(self, wrapped):
         self.wrapped = wrapped
 
     def __getitem__(self, name):
         if name == "_":
             return self.wrapped
         try:
             return getattr(self.wrapped, name)
         except AttributeError:
             raise KeyError(name)
 
 # Python 2.3 compatibility
 # use eval workaround to find out which names are used in the
 # eval string and put them into the locals. This works for most
 # normal uses case, bizarre ones like accessing the locals()
 # will fail
 try:
     eval("_", None, AttrNamespace(None))
 except TypeError:
     real_eval = eval
     def eval(codestring, _globals, _locals):
         """
         eval(source[, globals[, locals]]) -> value
 
         Evaluate the source in the context of globals and locals.
         The source may be a string representing a Python expression
         or a code object as returned by compile().
         The globals must be a dictionary and locals can be any mappping.
 
         This function is a workaround for the shortcomings of
         Python 2.3's eval.
         """
 
         if isinstance(codestring, basestring):
             code = compile(codestring, "_eval", "eval")
         else:
             code = codestring
         newlocals = {}
         for name in code.co_names:
             try:
                 newlocals[name] = _locals[name]
             except KeyError:
                 pass
         return real_eval(code, _globals, newlocals)
 
 
 noitem = object()
 
 
 def item(iterator, index, default=noitem):
     """
     Return the ``index``th item from the iterator ``iterator``.
     ``index`` must be an integer (negative integers are relative to the
     end (i.e. the last items produced by the iterator)).
 
     If ``default`` is given, this will be the default value when
     the iterator doesn't contain an item at this position. Otherwise an
     ``IndexError`` will be raised.
 
     Note that using this function will partially or totally exhaust the
     iterator.
     """
     i = index
     if i>=0:
         for item in iterator:
             if not i:
                 return item
             i -= 1
     else:
         i = -index
         cache = deque()
         for item in iterator:
             cache.append(item)
             if len(cache)>i:
                 cache.popleft()
         if len(cache)==i:
             return cache.popleft()
     if default is noitem:
         raise IndexError(index)
     else:
         return default
 
 
 def getglobals(g):
     """
     Return the global namespace that is used for expression strings in
     ``ifilter`` and others. This is ``g`` or (if ``g`` is ``None``) IPython's
     user namespace.
     """
     if g is None:
         if ipapi is not None:
             api = ipapi.get()
             if api is not None:
                 return api.user_ns
         return globals()
     return g
 
 
 class Descriptor(object):
     """
     A ``Descriptor`` object is used for describing the attributes of objects.
     """
     def __hash__(self):
         return hash(self.__class__) ^ hash(self.key())
 
     def __eq__(self, other):
         return self.__class__ is other.__class__ and self.key() == other.key()
 
     def __ne__(self, other):
         return self.__class__ is not other.__class__ or self.key() != other.key()
 
     def key(self):
         pass
 
     def name(self):
         """
         Return the name of this attribute for display by a ``Display`` object
         (e.g. as a column title).
         """
         key = self.key()
         if key is None:
             return "_"
         return str(key)
 
     def attrtype(self, obj):
         """
         Return the type of this attribute (i.e. something like "attribute" or
         "method").
         """
 
     def valuetype(self, obj):
         """
         Return the type of this attribute value of the object ``obj``.
         """
 
     def value(self, obj):
         """
         Return the value of this attribute of the object ``obj``.
         """
 
     def doc(self, obj):
         """
         Return the documentation for this attribute.
         """
 
     def shortdoc(self, obj):
         """
         Return a short documentation for this attribute (defaulting to the
         first line).
         """
         doc = self.doc(obj)
         if doc is not None:
             doc = doc.strip().splitlines()[0].strip()
         return doc
 
     def iter(self, obj):
         """
         Return an iterator for this attribute of the object ``obj``.
         """
         return xiter(self.value(obj))
 
 
 class SelfDescriptor(Descriptor):
     """
     A ``SelfDescriptor`` describes the object itself.
     """
     def key(self):
         return None
 
     def attrtype(self, obj):
         return "self"
 
     def valuetype(self, obj):
         return type(obj)
 
     def value(self, obj):
         return obj
 
     def __repr__(self):
         return "Self"
 
 selfdescriptor = SelfDescriptor() # there's no need for more than one
 
 
 class AttributeDescriptor(Descriptor):
     """
     An ``AttributeDescriptor`` describes a simple attribute of an object.
     """
     __slots__ = ("_name", "_doc")
 
     def __init__(self, name, doc=None):
         self._name = name
         self._doc = doc
 
     def key(self):
         return self._name
 
     def doc(self, obj):
         return self._doc
 
     def attrtype(self, obj):
         return "attr"
 
     def valuetype(self, obj):
         return type(getattr(obj, self._name))
 
     def value(self, obj):
         return getattr(obj, self._name)
 
     def __repr__(self):
         if self._doc is None:
             return "Attribute(%r)" % self._name
         else:
             return "Attribute(%r, %r)" % (self._name, self._doc)
 
 
 class IndexDescriptor(Descriptor):
     """
     An ``IndexDescriptor`` describes an "attribute" of an object that is fetched
     via ``__getitem__``.
     """
     __slots__ = ("_index",)
 
     def __init__(self, index):
         self._index = index
 
     def key(self):
         return self._index
 
     def attrtype(self, obj):
         return "item"
 
     def valuetype(self, obj):
         return type(obj[self._index])
 
     def value(self, obj):
         return obj[self._index]
 
     def __repr__(self):
         return "Index(%r)" % self._index
 
 
 class MethodDescriptor(Descriptor):
     """
     A ``MethodDescriptor`` describes a method of an object that can be called
     without argument. Note that this method shouldn't change the object.
     """
     __slots__ = ("_name", "_doc")
 
     def __init__(self, name, doc=None):
         self._name = name
         self._doc = doc
 
     def key(self):
         return self._name
 
     def doc(self, obj):
         if self._doc is None:
             return getattr(obj, self._name).__doc__
         return self._doc
 
     def attrtype(self, obj):
         return "method"
 
     def valuetype(self, obj):
         return type(self.value(obj))
 
     def value(self, obj):
         return getattr(obj, self._name)()
 
     def __repr__(self):
         if self._doc is None:
             return "Method(%r)" % self._name
         else:
             return "Method(%r, %r)" % (self._name, self._doc)
 
 
 class IterAttributeDescriptor(Descriptor):
     """
     An ``IterAttributeDescriptor`` works like an ``AttributeDescriptor`` but
     doesn't return an attribute values (because this value might be e.g. a large
     list).
     """
     __slots__ = ("_name", "_doc")
 
     def __init__(self, name, doc=None):
         self._name = name
         self._doc = doc
 
     def key(self):
         return self._name
 
     def doc(self, obj):
         return self._doc
 
     def attrtype(self, obj):
         return "iter"
 
     def valuetype(self, obj):
         return noitem
 
     def value(self, obj):
         return noitem
 
     def iter(self, obj):
         return xiter(getattr(obj, self._name))
 
     def __repr__(self):
         if self._doc is None:
             return "IterAttribute(%r)" % self._name
         else:
             return "IterAttribute(%r, %r)" % (self._name, self._doc)
 
 
 class IterMethodDescriptor(Descriptor):
     """
     An ``IterMethodDescriptor`` works like an ``MethodDescriptor`` but doesn't
     return an attribute values (because this value might be e.g. a large list).
     """
     __slots__ = ("_name", "_doc")
 
     def __init__(self, name, doc=None):
         self._name = name
         self._doc = doc
 
     def key(self):
         return self._name
 
     def doc(self, obj):
         if self._doc is None:
             return getattr(obj, self._name).__doc__
         return self._doc
 
     def attrtype(self, obj):
         return "itermethod"
 
     def valuetype(self, obj):
         return noitem
 
     def value(self, obj):
         return noitem
 
     def iter(self, obj):
         return xiter(getattr(obj, self._name)())
 
     def __repr__(self):
         if self._doc is None:
             return "IterMethod(%r)" % self._name
         else:
             return "IterMethod(%r, %r)" % (self._name, self._doc)
 
 
 class FunctionDescriptor(Descriptor):
     """
     A ``FunctionDescriptor`` turns a function into a descriptor. The function
     will be called with the object to get the type and value of the attribute.
     """
     __slots__ = ("_function", "_name", "_doc")
 
     def __init__(self, function, name=None, doc=None):
         self._function = function
         self._name = name
         self._doc = doc
 
     def key(self):
         return self._function
 
     def name(self):
         if self._name is not None:
             return self._name
         return getattr(self._function, "__xname__", self._function.__name__)
 
     def doc(self, obj):
         if self._doc is None:
             return self._function.__doc__
         return self._doc
 
     def attrtype(self, obj):
         return "function"
 
     def valuetype(self, obj):
         return type(self._function(obj))
 
     def value(self, obj):
         return self._function(obj)
 
     def __repr__(self):
         if self._doc is None:
             return "Function(%r)" % self._name
         else:
             return "Function(%r, %r)" % (self._name, self._doc)
 
 
 class Table(object):
     """
     A ``Table`` is an object that produces items (just like a normal Python
     iterator/generator does) and can be used as the first object in a pipeline
     expression. The displayhook will open the default browser for such an object
     (instead of simply printing the ``repr()`` result).
     """
 
     # We want to support ``foo`` and ``foo()`` in pipeline expression:
     # So we implement the required operators (``|`` and ``+``) in the metaclass,
     # instantiate the class and forward the operator to the instance
     class __metaclass__(type):
         def __iter__(self):
             return iter(self())
 
         def __or__(self, other):
             return self() | other
 
         def __add__(self, other):
             return self() + other
 
         def __radd__(self, other):
             return other + self()
 
         def __getitem__(self, index):
             return self()[index]
 
     def __getitem__(self, index):
         return item(self, index)
 
     def __contains__(self, item):
         for haveitem in self:
             if item == haveitem:
                 return True
         return False
 
     def __or__(self, other):
         # autoinstantiate right hand side
         if isinstance(other, type) and issubclass(other, (Table, Display)):
             other = other()
         # treat simple strings and functions as ``ieval`` instances
         elif not isinstance(other, Display) and not isinstance(other, Table):
             other = ieval(other)
         # forward operations to the right hand side
         return other.__ror__(self)
 
     def __add__(self, other):
         # autoinstantiate right hand side
         if isinstance(other, type) and issubclass(other, Table):
             other = other()
         return ichain(self, other)
 
     def __radd__(self, other):
         # autoinstantiate left hand side
         if isinstance(other, type) and issubclass(other, Table):
             other = other()
         return ichain(other, self)
 
 
 class Pipe(Table):
     """
     A ``Pipe`` is an object that can be used in a pipeline expression. It
     processes the objects it gets from its input ``Table``/``Pipe``. Note that
     a ``Pipe`` object can't be used as the first object in a pipeline
     expression, as it doesn't produces items itself.
     """
     class __metaclass__(Table.__metaclass__):
         def __ror__(self, input):
             return input | self()
 
     def __ror__(self, input):
         # autoinstantiate left hand side
         if isinstance(input, type) and issubclass(input, Table):
             input = input()
         self.input = input
         return self
 
 
 def xrepr(item, mode="default"):
     """
     Generic function that adds color output and different display modes to ``repr``.
 
     The result of an ``xrepr`` call is iterable and consists of ``(style, string)``
     tuples. The ``style`` in this tuple must be a ``Style`` object from the
     ``astring`` module. To reconfigure the output the first yielded tuple can be
     a ``(aligment, full)`` tuple instead of a ``(style, string)`` tuple.
     ``alignment``  can be -1 for left aligned, 0 for centered and 1 for right
     aligned (the default is left alignment). ``full`` is a boolean that specifies
     whether the complete output must be displayed or the ``Display`` object is
     allowed to stop output after enough text has been produced (e.g. a syntax
     highlighted text line would use ``True``, but for a large data structure
     (i.e. a nested list, tuple or dictionary) ``False`` would be used).
     The default is full output.
 
     There are four different possible values for ``mode`` depending on where
     the ``Display`` object will display ``item``:
 
     ``"header"``
         ``item`` will be displayed in a header line (this is used by ``ibrowse``).
 
     ``"footer"``
         ``item`` will be displayed in a footer line (this is used by ``ibrowse``).
 
     ``"cell"``
         ``item`` will be displayed in a table cell/list.
 
     ``"default"``
         default mode. If an ``xrepr`` implementation recursively outputs objects,
         ``"default"`` must be passed in the recursive calls to ``xrepr``.
 
     If no implementation is registered for ``item``, ``xrepr`` will try the
     ``__xrepr__`` method on ``item``. If ``item`` doesn't have an ``__xrepr__``
     method it falls back to ``repr``/``__repr__`` for all modes.
     """
     try:
         func = item.__xrepr__
     except AttributeError:
         yield (astyle.style_default, repr(item))
     else:
         try:
             for x in func(mode):
                 yield x
-        except (KeyboardInterrupt, SystemExit):
+        except (KeyboardInterrupt, SystemExit, GeneratorExit):
             raise
         except Exception:
             yield (astyle.style_default, repr(item))
 xrepr = simplegeneric.generic(xrepr)
 
 
 def xrepr_none(self, mode="default"):
     yield (astyle.style_type_none, repr(self))
 xrepr.when_object(None)(xrepr_none)
 
 
 def xrepr_noitem(self, mode="default"):
     yield (2, True)
     yield (astyle.style_nodata, "<?>")
 xrepr.when_object(noitem)(xrepr_noitem)
 
 
 def xrepr_bool(self, mode="default"):
     yield (astyle.style_type_bool, repr(self))
 xrepr.when_type(bool)(xrepr_bool)
 
 
 def xrepr_str(self, mode="default"):
     if mode == "cell":
         yield (astyle.style_default, repr(self.expandtabs(tab))[1:-1])
     else:
         yield (astyle.style_default, repr(self))
 xrepr.when_type(str)(xrepr_str)
 
 
 def xrepr_unicode(self, mode="default"):
     if mode == "cell":
         yield (astyle.style_default, repr(self.expandtabs(tab))[2:-1])
     else:
         yield (astyle.style_default, repr(self))
 xrepr.when_type(unicode)(xrepr_unicode)
 
 
 def xrepr_number(self, mode="default"):
     yield (1, True)
     yield (astyle.style_type_number, repr(self))
 xrepr.when_type(int)(xrepr_number)
 xrepr.when_type(long)(xrepr_number)
 xrepr.when_type(float)(xrepr_number)
 
 
 def xrepr_complex(self, mode="default"):
     yield (astyle.style_type_number, repr(self))
 xrepr.when_type(complex)(xrepr_number)
 
 
 def xrepr_datetime(self, mode="default"):
     if mode == "cell":
         # Don't use strftime() here, as this requires year >= 1900
         yield (astyle.style_type_datetime,
                "%04d-%02d-%02d %02d:%02d:%02d.%06d" % \
                     (self.year, self.month, self.day,
                      self.hour, self.minute, self.second,
                      self.microsecond),
                 )
     else:
         yield (astyle.style_type_datetime, repr(self))
 xrepr.when_type(datetime.datetime)(xrepr_datetime)
 
 
 def xrepr_date(self, mode="default"):
     if mode == "cell":
         yield (astyle.style_type_datetime,
                "%04d-%02d-%02d" % (self.year, self.month, self.day))
     else:
         yield (astyle.style_type_datetime, repr(self))
 xrepr.when_type(datetime.date)(xrepr_date)
 
 
 def xrepr_time(self, mode="default"):
     if mode == "cell":
         yield (astyle.style_type_datetime,
                 "%02d:%02d:%02d.%06d" % \
                     (self.hour, self.minute, self.second, self.microsecond))
     else:
         yield (astyle.style_type_datetime, repr(self))
 xrepr.when_type(datetime.time)(xrepr_time)
 
 
 def xrepr_timedelta(self, mode="default"):
     yield (astyle.style_type_datetime, repr(self))
 xrepr.when_type(datetime.timedelta)(xrepr_timedelta)
 
 
 def xrepr_type(self, mode="default"):
     if self.__module__ == "__builtin__":
         yield (astyle.style_type_type, self.__name__)
     else:
         yield (astyle.style_type_type, "%s.%s" % (self.__module__, self.__name__))
 xrepr.when_type(type)(xrepr_type)
 
 
 def xrepr_exception(self, mode="default"):
     if self.__class__.__module__ == "exceptions":
         classname = self.__class__.__name__
     else:
         classname = "%s.%s" % \
             (self.__class__.__module__, self.__class__.__name__)
     if mode == "header" or mode == "footer":
         yield (astyle.style_error, "%s: %s" % (classname, self))
     else:
         yield (astyle.style_error, classname)
 xrepr.when_type(Exception)(xrepr_exception)
 
 
 def xrepr_listtuple(self, mode="default"):
     if mode == "header" or mode == "footer":
         if self.__class__.__module__ == "__builtin__":
             classname = self.__class__.__name__
         else:
             classname = "%s.%s" % \
                 (self.__class__.__module__,self.__class__.__name__)
         yield (astyle.style_default,
                "<%s object with %d items at 0x%x>" % \
                    (classname, len(self), id(self)))
     else:
         yield (-1, False)
         if isinstance(self, list):
             yield (astyle.style_default, "[")
             end = "]"
         else:
             yield (astyle.style_default, "(")
             end = ")"
         for (i, subself) in enumerate(self):
             if i:
                 yield (astyle.style_default, ", ")
             for part in xrepr(subself, "default"):
                 yield part
         yield (astyle.style_default, end)
 xrepr.when_type(list)(xrepr_listtuple)
 xrepr.when_type(tuple)(xrepr_listtuple)
 
 
 def xrepr_dict(self, mode="default"):
     if mode == "header" or mode == "footer":
         if self.__class__.__module__ == "__builtin__":
             classname = self.__class__.__name__
         else:
             classname = "%s.%s" % \
                 (self.__class__.__module__,self.__class__.__name__)
         yield (astyle.style_default,
                "<%s object with %d items at 0x%x>" % \
                 (classname, len(self), id(self)))
     else:
         yield (-1, False)
         if isinstance(self, dict):
             yield (astyle.style_default, "{")
             end = "}"
         else:
             yield (astyle.style_default, "dictproxy((")
             end = "})"
         for (i, (key, value)) in enumerate(self.iteritems()):
             if i:
                 yield (astyle.style_default, ", ")
             for part in xrepr(key, "default"):
                 yield part
             yield (astyle.style_default, ": ")
             for part in xrepr(value, "default"):
                 yield part
         yield (astyle.style_default, end)
 xrepr.when_type(dict)(xrepr_dict)
 xrepr.when_type(types.DictProxyType)(xrepr_dict)
 
 
 def upgradexattr(attr):
     """
     Convert an attribute descriptor string to a real descriptor object.
 
-    If attr already is a descriptor object return if unmodified. A
+    If attr already is a descriptor object return it unmodified. A
     ``SelfDescriptor`` will be returned if ``attr`` is ``None``. ``"foo"``
     returns an ``AttributeDescriptor`` for the attribute named ``"foo"``.
     ``"foo()"`` returns a ``MethodDescriptor`` for the method named ``"foo"``.
     ``"-foo"`` will return an ``IterAttributeDescriptor`` for the attribute
     named ``"foo"`` and ``"-foo()"`` will return an ``IterMethodDescriptor``
-    for the method named ``"foo"``. Furthermore integer will return the appropriate
+    for the method named ``"foo"``. Furthermore integers will return the appropriate
     ``IndexDescriptor`` and callables will return a ``FunctionDescriptor``.
     """
     if attr is None:
         return selfdescriptor
     elif isinstance(attr, Descriptor):
         return attr
-    elif isinstance(attr, str):
+    elif isinstance(attr, basestring):
         if attr.endswith("()"):
             if attr.startswith("-"):
                 return IterMethodDescriptor(attr[1:-2])
             else:
                 return MethodDescriptor(attr[:-2])
         else:
             if attr.startswith("-"):
                 return IterAttributeDescriptor(attr[1:])
             else:
                 return AttributeDescriptor(attr)
     elif isinstance(attr, (int, long)):
         return IndexDescriptor(attr)
     elif callable(attr):
         return FunctionDescriptor(attr)
     else:
         raise TypeError("can't handle descriptor %r" % attr)
 
 
 def xattrs(item, mode="default"):
     """
     Generic function that returns an iterable of attribute descriptors
     to be used for displaying the attributes ob the object ``item`` in display
     mode ``mode``.
 
     There are two possible modes:
 
     ``"detail"``
         The ``Display`` object wants to display a detailed list of the object
         attributes.
 
     ``"default"``
         The ``Display`` object wants to display the object in a list view.
 
     If no implementation is registered for the object ``item`` ``xattrs`` falls
     back to trying the ``__xattrs__`` method of the object. If this doesn't
     exist either, ``dir(item)`` is used for ``"detail"`` mode and ``(None,)``
     for ``"default"`` mode.
 
     The implementation must yield attribute descriptors (see the class
     ``Descriptor`` for more info). The ``__xattrs__`` method may also return
     attribute descriptor strings (and ``None``) which will be converted to real
     descriptors by ``upgradexattr()``.
     """
     try:
         func = item.__xattrs__
     except AttributeError:
         if mode == "detail":
             for attrname in dir(item):
                 yield AttributeDescriptor(attrname)
         else:
             yield selfdescriptor
     else:
         for attr in func(mode):
             yield upgradexattr(attr)
 xattrs = simplegeneric.generic(xattrs)
 
 
 def xattrs_complex(self, mode="default"):
     if mode == "detail":
         return (AttributeDescriptor("real"), AttributeDescriptor("imag"))
     return (selfdescriptor,)
 xattrs.when_type(complex)(xattrs_complex)
 
 
 def _isdict(item):
     try:
         itermeth = item.__class__.__iter__
     except (AttributeError, TypeError):
         return False
     return itermeth is dict.__iter__ or itermeth is types.DictProxyType.__iter__
 
 
 def _isstr(item):
     if not isinstance(item, basestring):
         return False
     try:
         itermeth = item.__class__.__iter__
     except AttributeError:
         return True
     return False # ``__iter__`` has been redefined
 
 
 def xiter(item):
     """
     Generic function that implements iteration for pipeline expression. If no
     implementation is registered for ``item`` ``xiter`` falls back to ``iter``.
     """
     try:
         func = item.__xiter__
     except AttributeError:
         if _isdict(item):
             def items(item):
                 fields = ("key", "value")
                 for (key, value) in item.iteritems():
                     yield Fields(fields, key=key, value=value)
             return items(item)
         elif isinstance(item, new.module):
             def items(item):
                 fields = ("key", "value")
                 for key in sorted(item.__dict__):
                     yield Fields(fields, key=key, value=getattr(item, key))
             return items(item)
         elif _isstr(item):
             if not item:
                 raise ValueError("can't enter empty string")
             lines = item.splitlines()
             if len(lines) == 1:
                def iterone(item):
                    yield item
                return iterone(item)
             else:
                 return iter(lines)
         return iter(item)
     else:
         return iter(func()) # iter() just to be safe
 xiter = simplegeneric.generic(xiter)
 
 
 class ichain(Pipe):
     """
     Chains multiple ``Table``s into one.
     """
 
     def __init__(self, *iters):
         self.iters = iters
 
     def __iter__(self):
         return itertools.chain(*self.iters)
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             for (i, item) in enumerate(self.iters):
                 if i:
                     yield (astyle.style_default, "+")
                 if isinstance(item, Pipe):
                     yield (astyle.style_default, "(")
                 for part in xrepr(item, mode):
                     yield part
                 if isinstance(item, Pipe):
                     yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         args = ", ".join([repr(it) for it in self.iters])
         return "%s.%s(%s)" % \
             (self.__class__.__module__, self.__class__.__name__, args)
 
 
 class ifile(path.path):
     """
     file (or directory) object.
     """
 
     def getmode(self):
         return self.stat().st_mode
     mode = property(getmode, None, None, "Access mode")
 
     def gettype(self):
         data = [
             (stat.S_ISREG, "file"),
             (stat.S_ISDIR, "dir"),
             (stat.S_ISCHR, "chardev"),
             (stat.S_ISBLK, "blockdev"),
             (stat.S_ISFIFO, "fifo"),
             (stat.S_ISLNK, "symlink"),
             (stat.S_ISSOCK,"socket"),
         ]
         lstat = self.lstat()
         if lstat is not None:
             types = set([text for (func, text) in data if func(lstat.st_mode)])
         else:
             types = set()
         m = self.mode
         types.update([text for (func, text) in data if func(m)])
         return ", ".join(types)
     type = property(gettype, None, None, "file type (file, directory, link, etc.)")
 
     def getmodestr(self):
         m = self.mode
         data = [
             (stat.S_IRUSR, "-r"),
             (stat.S_IWUSR, "-w"),
             (stat.S_IXUSR, "-x"),
             (stat.S_IRGRP, "-r"),
             (stat.S_IWGRP, "-w"),
             (stat.S_IXGRP, "-x"),
             (stat.S_IROTH, "-r"),
             (stat.S_IWOTH, "-w"),
             (stat.S_IXOTH, "-x"),
         ]
         return "".join([text[bool(m&bit)] for (bit, text) in data])
 
     modestr = property(getmodestr, None, None, "Access mode as string")
 
     def getblocks(self):
         return self.stat().st_blocks
     blocks = property(getblocks, None, None, "File size in blocks")
 
     def getblksize(self):
         return self.stat().st_blksize
     blksize = property(getblksize, None, None, "Filesystem block size")
 
     def getdev(self):
         return self.stat().st_dev
     dev = property(getdev)
 
     def getnlink(self):
         return self.stat().st_nlink
     nlink = property(getnlink, None, None, "Number of links")
 
     def getuid(self):
         return self.stat().st_uid
     uid = property(getuid, None, None, "User id of file owner")
 
     def getgid(self):
         return self.stat().st_gid
     gid = property(getgid, None, None, "Group id of file owner")
 
     def getowner(self):
         stat = self.stat()
         try:
             return pwd.getpwuid(stat.st_uid).pw_name
         except KeyError:
             return stat.st_uid
     owner = property(getowner, None, None, "Owner name (or id)")
 
     def getgroup(self):
         stat = self.stat()
         try:
             return grp.getgrgid(stat.st_gid).gr_name
         except KeyError:
             return stat.st_gid
     group = property(getgroup, None, None, "Group name (or id)")
 
     def getadate(self):
         return datetime.datetime.utcfromtimestamp(self.atime)
     adate = property(getadate, None, None, "Access date")
 
     def getcdate(self):
         return datetime.datetime.utcfromtimestamp(self.ctime)
     cdate = property(getcdate, None, None, "Creation date")
 
     def getmdate(self):
         return datetime.datetime.utcfromtimestamp(self.mtime)
     mdate = property(getmdate, None, None, "Modification date")
 
     def mimetype(self):
         """
         Return MIME type guessed from the extension.
         """
         return mimetypes.guess_type(self.basename())[0]
 
     def encoding(self):
         """
         Return guessed compression (like "compress" or "gzip").
         """
         return mimetypes.guess_type(self.basename())[1]
 
     def __repr__(self):
         return "ifile(%s)" % path._base.__repr__(self)
 
     if sys.platform == "win32":
         defaultattrs = (None, "type", "size", "modestr", "mdate")
     else:
         defaultattrs = (None, "type", "size", "modestr", "owner", "group", "mdate")
 
     def __xattrs__(self, mode="default"):
         if mode == "detail":
             return (
                 "name",
                 "basename()",
                 "abspath()",
                 "realpath()",
                 "type",
                 "mode",
                 "modestr",
                 "stat()",
                 "lstat()",
                 "uid",
                 "gid",
                 "owner",
                 "group",
                 "dev",
                 "nlink",
                 "ctime",
                 "mtime",
                 "atime",
                 "cdate",
                 "mdate",
                 "adate",
                 "size",
                 "blocks",
                 "blksize",
                 "isdir()",
                 "islink()",
                 "mimetype()",
                 "encoding()",
                 "-listdir()",
                 "-dirs()",
                 "-files()",
                 "-walk()",
                 "-walkdirs()",
                 "-walkfiles()",
             )
         else:
             return self.defaultattrs
 
 
 def xiter_ifile(self):
     if self.isdir():
         yield (self / os.pardir).abspath()
         for child in sorted(self.listdir()):
             yield child
     else:
         f = self.open("rb")
         for line in f:
             yield line
         f.close()
 xiter.when_type(ifile)(xiter_ifile)
 
 
 # We need to implement ``xrepr`` for ``ifile`` as a generic function, because
 # otherwise ``xrepr_str`` would kick in.
 def xrepr_ifile(self, mode="default"):
     try:
         if self.isdir():
             name = "idir"
             style = astyle.style_dir
         else:
             name = "ifile"
             style = astyle.style_file
     except IOError:
         name = "ifile"
         style = astyle.style_default
     if mode in ("cell", "header", "footer"):
         abspath = repr(path._base(self.normpath()))
         if abspath.startswith("u"):
             abspath = abspath[2:-1]
         else:
             abspath = abspath[1:-1]
         if mode == "cell":
             yield (style, abspath)
         else:
             yield (style, "%s(%s)" % (name, abspath))
     else:
         yield (style, repr(self))
 xrepr.when_type(ifile)(xrepr_ifile)
 
 
 class ils(Table):
     """
     List the current (or a specified) directory.
 
     Examples::
 
         >>> ils
         <class 'IPython.Extensions.ipipe.ils'>
         >>> ils("/usr/local/lib/python2.4")
         IPython.Extensions.ipipe.ils('/usr/local/lib/python2.4')
         >>> ils("~")
         IPython.Extensions.ipipe.ils('/home/fperez')
         # all-random
     """
     def __init__(self, base=os.curdir, dirs=True, files=True):
         self.base = os.path.expanduser(base)
         self.dirs = dirs
         self.files = files
 
     def __iter__(self):
         base = ifile(self.base)
         yield (base / os.pardir).abspath()
         for child in sorted(base.listdir()):
             if self.dirs:
                 if self.files:
                     yield child
                 else:
                     if child.isdir():
                         yield child
             elif self.files:
                 if not child.isdir():
                     yield child
 
     def __xrepr__(self, mode="default"):
        return xrepr(ifile(self.base), mode)
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self.base)
 
 
 class iglob(Table):
     """
     List all files and directories matching a specified pattern.
     (See ``glob.glob()`` for more info.).
 
     Examples::
 
         >>> iglob("*.py")
         IPython.Extensions.ipipe.iglob('*.py')
     """
     def __init__(self, glob):
         self.glob = glob
 
     def __iter__(self):
         for name in glob.glob(self.glob):
             yield ifile(name)
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer" or mode == "cell":
             yield (astyle.style_default,
                    "%s(%r)" % (self.__class__.__name__, self.glob))
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self.glob)
 
 
 class iwalk(Table):
     """
     List all files and directories in a directory and it's subdirectory::
 
         >>> iwalk
         <class 'IPython.Extensions.ipipe.iwalk'>
         >>> iwalk("/usr/lib")
         IPython.Extensions.ipipe.iwalk('/usr/lib')
         >>> iwalk("~")
         IPython.Extensions.ipipe.iwalk('/home/fperez')  # random
         
     """
     def __init__(self, base=os.curdir, dirs=True, files=True):
         self.base = os.path.expanduser(base)
         self.dirs = dirs
         self.files = files
 
     def __iter__(self):
         for (dirpath, dirnames, filenames) in os.walk(self.base):
             if self.dirs:
                 for name in sorted(dirnames):
                     yield ifile(os.path.join(dirpath, name))
             if self.files:
                 for name in sorted(filenames):
                     yield ifile(os.path.join(dirpath, name))
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer" or mode == "cell":
             yield (astyle.style_default,
                    "%s(%r)" % (self.__class__.__name__, self.base))
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self.base)
 
 
 class ipwdentry(object):
     """
     ``ipwdentry`` objects encapsulate entries in the Unix user account and
     password database.
     """
     def __init__(self, id):
         self._id = id
         self._entry = None
 
     def __eq__(self, other):
         return self.__class__ is other.__class__ and self._id == other._id
 
     def __ne__(self, other):
         return self.__class__ is not other.__class__ or self._id != other._id
 
     def _getentry(self):
         if self._entry is None:
             if isinstance(self._id, basestring):
                 self._entry = pwd.getpwnam(self._id)
             else:
                 self._entry = pwd.getpwuid(self._id)
         return self._entry
 
     def getname(self):
         if isinstance(self._id, basestring):
             return self._id
         else:
             return self._getentry().pw_name
     name = property(getname, None, None, "User name")
 
     def getpasswd(self):
         return self._getentry().pw_passwd
     passwd = property(getpasswd, None, None, "Password")
 
     def getuid(self):
         if isinstance(self._id, basestring):
             return self._getentry().pw_uid
         else:
             return self._id
     uid = property(getuid, None, None, "User id")
 
     def getgid(self):
         return self._getentry().pw_gid
     gid = property(getgid, None, None, "Primary group id")
 
     def getgroup(self):
         return igrpentry(self.gid)
     group = property(getgroup, None, None, "Group")
 
     def getgecos(self):
         return self._getentry().pw_gecos
     gecos = property(getgecos, None, None, "Information (e.g. full user name)")
 
     def getdir(self):
         return self._getentry().pw_dir
     dir = property(getdir, None, None, "$HOME directory")
 
     def getshell(self):
         return self._getentry().pw_shell
     shell = property(getshell, None, None, "Login shell")
 
     def __xattrs__(self, mode="default"):
        return ("name", "passwd", "uid", "gid", "gecos", "dir", "shell")
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self._id)
 
 
 class ipwd(Table):
     """
     List all entries in the Unix user account and password database.
 
     Example::
 
         >>> ipwd | isort("uid")
         <IPython.Extensions.ipipe.isort key='uid' reverse=False at 0x849efec>
         # random
     """
     def __iter__(self):
         for entry in pwd.getpwall():
             yield ipwdentry(entry.pw_name)
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer" or mode == "cell":
             yield (astyle.style_default, "%s()" % self.__class__.__name__)
         else:
             yield (astyle.style_default, repr(self))
 
 
 class igrpentry(object):
     """
     ``igrpentry`` objects encapsulate entries in the Unix group database.
     """
     def __init__(self, id):
         self._id = id
         self._entry = None
 
     def __eq__(self, other):
         return self.__class__ is other.__class__ and self._id == other._id
 
     def __ne__(self, other):
         return self.__class__ is not other.__class__ or self._id != other._id
 
     def _getentry(self):
         if self._entry is None:
             if isinstance(self._id, basestring):
                 self._entry = grp.getgrnam(self._id)
             else:
                 self._entry = grp.getgrgid(self._id)
         return self._entry
 
     def getname(self):
         if isinstance(self._id, basestring):
             return self._id
         else:
             return self._getentry().gr_name
     name = property(getname, None, None, "Group name")
 
     def getpasswd(self):
         return self._getentry().gr_passwd
     passwd = property(getpasswd, None, None, "Password")
 
     def getgid(self):
         if isinstance(self._id, basestring):
             return self._getentry().gr_gid
         else:
             return self._id
     gid = property(getgid, None, None, "Group id")
 
     def getmem(self):
         return self._getentry().gr_mem
     mem = property(getmem, None, None, "Members")
 
     def __xattrs__(self, mode="default"):
         return ("name", "passwd", "gid", "mem")
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer" or mode == "cell":
             yield (astyle.style_default, "group ")
             try:
                 yield (astyle.style_default, self.name)
             except KeyError:
                 if isinstance(self._id, basestring):
                     yield (astyle.style_default, self.name_id)
                 else:
                     yield (astyle.style_type_number, str(self._id))
         else:
             yield (astyle.style_default, repr(self))
 
     def __iter__(self):
         for member in self.mem:
             yield ipwdentry(member)
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self._id)
 
 
 class igrp(Table):
     """
     This ``Table`` lists all entries in the Unix group database.
     """
     def __iter__(self):
         for entry in grp.getgrall():
             yield igrpentry(entry.gr_name)
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             yield (astyle.style_default, "%s()" % self.__class__.__name__)
         else:
             yield (astyle.style_default, repr(self))
 
 
 class Fields(object):
     def __init__(self, fieldnames, **fields):
         self.__fieldnames = [upgradexattr(fieldname) for fieldname in fieldnames]
         for (key, value) in fields.iteritems():
             setattr(self, key, value)
 
     def __xattrs__(self, mode="default"):
         return self.__fieldnames
 
     def __xrepr__(self, mode="default"):
         yield (-1, False)
         if mode == "header" or mode == "cell":
             yield (astyle.style_default, self.__class__.__name__)
             yield (astyle.style_default, "(")
             for (i, f) in enumerate(self.__fieldnames):
                 if i:
                     yield (astyle.style_default, ", ")
                 yield (astyle.style_default, f.name())
                 yield (astyle.style_default, "=")
                 for part in xrepr(getattr(self, f), "default"):
                     yield part
             yield (astyle.style_default, ")")
         elif mode == "footer":
             yield (astyle.style_default, self.__class__.__name__)
             yield (astyle.style_default, "(")
             for (i, f) in enumerate(self.__fieldnames):
                 if i:
                     yield (astyle.style_default, ", ")
                 yield (astyle.style_default, f.name())
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
 
 class FieldTable(Table, list):
     def __init__(self, *fields):
         Table.__init__(self)
         list.__init__(self)
         self.fields = fields
 
     def add(self, **fields):
         self.append(Fields(self.fields, **fields))
 
     def __xrepr__(self, mode="default"):
         yield (-1, False)
         if mode == "header" or mode == "footer":
             yield (astyle.style_default, self.__class__.__name__)
             yield (astyle.style_default, "(")
             for (i, f) in enumerate(self.__fieldnames):
                 if i:
                     yield (astyle.style_default, ", ")
                 yield (astyle.style_default, f)
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "<%s.%s object with fields=%r at 0x%x>" % \
             (self.__class__.__module__, self.__class__.__name__,
              ", ".join(map(repr, self.fields)), id(self))
 
 
 class List(list):
     def __xattrs__(self, mode="default"):
         return xrange(len(self))
 
     def __xrepr__(self, mode="default"):
         yield (-1, False)
         if mode == "header" or mode == "cell" or mode == "footer" or mode == "default":
             yield (astyle.style_default, self.__class__.__name__)
             yield (astyle.style_default, "(")
             for (i, item) in enumerate(self):
                 if i:
                     yield (astyle.style_default, ", ")
                 for part in xrepr(item, "default"):
                     yield part
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
 
 class ienv(Table):
     """
     List environment variables.
 
     Example::
 
         >>> ienv
         <class 'IPython.Extensions.ipipe.ienv'>
     """
 
     def __iter__(self):
         fields = ("key", "value")
         for (key, value) in os.environ.iteritems():
             yield Fields(fields, key=key, value=value)
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "cell":
             yield (astyle.style_default, "%s()" % self.__class__.__name__)
         else:
             yield (astyle.style_default, repr(self))
 
 
 class ihist(Table):
     """
     IPython input history
 
     Example::
 
         >>> ihist
         <class 'IPython.Extensions.ipipe.ihist'>
         >>> ihist(True) # raw mode
         <IPython.Extensions.ipipe.ihist object at 0x849602c>  # random
     """
     def __init__(self, raw=True):
         self.raw = raw
 
     def __iter__(self):
         api = ipapi.get()
         if self.raw:
             for line in api.IP.input_hist_raw:
                 yield line.rstrip("\n")
         else:
             for line in api.IP.input_hist:
                 yield line.rstrip("\n")
 
 
 class Alias(object):
     """
     Entry in the alias table
     """
     def __init__(self, name, args, command):
         self.name = name
         self.args = args
         self.command = command
 
     def __xattrs__(self, mode="default"):
         return ("name", "args", "command")
 
 
 class ialias(Table):
     """
     IPython alias list
 
     Example::
 
         >>> ialias
         <class 'IPython.Extensions.ipipe.ialias'>
     """
     def __iter__(self):
         api = ipapi.get()
 
         for (name, (args, command)) in api.IP.alias_table.iteritems():
             yield Alias(name, args, command)
 
 
 class icsv(Pipe):
     """
     This ``Pipe`` turns the input (with must be a pipe outputting lines
     or an ``ifile``) into lines of CVS columns.
     """
     def __init__(self, **csvargs):
         """
         Create an ``icsv`` object. ``cvsargs`` will be passed through as
         keyword arguments to ``cvs.reader()``.
         """
         self.csvargs = csvargs
 
     def __iter__(self):
         input = self.input
         if isinstance(input, ifile):
             input = input.open("rb")
         reader = csv.reader(input, **self.csvargs)
         for line in reader:
             yield List(line)
 
     def __xrepr__(self, mode="default"):
         yield (-1, False)
         if mode == "header" or mode == "footer":
             input = getattr(self, "input", None)
             if input is not None:
                 for part in xrepr(input, mode):
                     yield part
                 yield (astyle.style_default, " | ")
             yield (astyle.style_default, "%s(" % self.__class__.__name__)
             for (i, (name, value)) in enumerate(self.csvargs.iteritems()):
                 if i:
                     yield (astyle.style_default, ", ")
                 yield (astyle.style_default, name)
                 yield (astyle.style_default, "=")
                 for part in xrepr(value, "default"):
                     yield part
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         args = ", ".join(["%s=%r" % item for item in self.csvargs.iteritems()])
         return "<%s.%s %s at 0x%x>" % \
         (self.__class__.__module__, self.__class__.__name__, args, id(self))
 
 
 class ix(Table):
     """
     Execute a system command and list its output as lines
     (similar to ``os.popen()``).
 
     Examples::
 
         >>> ix("ps x")
         IPython.Extensions.ipipe.ix('ps x')
 
         >>> ix("find .") | ifile
         <IPython.Extensions.ipipe.ieval expr=<class 'IPython.Extensions.ipipe.ifile'> at 0x8509d2c>
         # random
     """
     def __init__(self, cmd):
         self.cmd = cmd
         self._pipeout = None
 
     def __iter__(self):
         (_pipein, self._pipeout) = os.popen4(self.cmd)
         _pipein.close()
         for l in self._pipeout:
             yield l.rstrip("\r\n")
         self._pipeout.close()
         self._pipeout = None
 
     def __del__(self):
         if self._pipeout is not None and not self._pipeout.closed:
             self._pipeout.close()
         self._pipeout = None
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             yield (astyle.style_default,
                    "%s(%r)" % (self.__class__.__name__, self.cmd))
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self.cmd)
 
 
 class ifilter(Pipe):
     """
     Filter an input pipe. Only objects where an expression evaluates to true
     (and doesn't raise an exception) are listed.
 
     Examples::
 
         >>> ils | ifilter("_.isfile() and size>1000")
         >>> igrp | ifilter("len(mem)")
         >>> sys.modules | ifilter(lambda _:_.value is not None)
         # all-random
     """
 
     def __init__(self, expr, globals=None, errors="raiseifallfail"):
         """
         Create an ``ifilter`` object. ``expr`` can be a callable or a string
         containing an expression. ``globals`` will be used as the global
         namespace for calling string expressions (defaulting to IPython's
         user namespace). ``errors`` specifies how exception during evaluation
         of ``expr`` are handled:
 
         ``"drop"``
             drop all items that have errors;
 
         ``"keep"``
             keep all items that have errors;
 
         ``"keeperror"``
             keep the exception of all items that have errors;
 
         ``"raise"``
             raise the exception;
 
         ``"raiseifallfail"``
             raise the first exception if all items have errors; otherwise drop
             those with errors (this is the default).
         """
         self.expr = expr
         self.globals = globals
         self.errors = errors
 
     def __iter__(self):
         if callable(self.expr):
             test = self.expr
         else:
             g = getglobals(self.globals)
             expr = compile(self.expr, "ipipe-expression", "eval")
             def test(item):
                 return eval(expr, g, AttrNamespace(item))
 
         ok = 0
         exc_info = None
         for item in xiter(self.input):
             try:
                 if test(item):
                     yield item
                 ok += 1
             except (KeyboardInterrupt, SystemExit):
                 raise
             except Exception, exc:
                 if self.errors == "drop":
                     pass # Ignore errors
                 elif self.errors == "keep":
                     yield item
                 elif self.errors == "keeperror":
                     yield exc
                 elif self.errors == "raise":
                     raise
                 elif self.errors == "raiseifallfail":
                     if exc_info is None:
                         exc_info = sys.exc_info()
         if not ok and exc_info is not None:
             raise exc_info[0], exc_info[1], exc_info[2]
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             input = getattr(self, "input", None)
             if input is not None:
                 for part in xrepr(input, mode):
                     yield part
                 yield (astyle.style_default, " | ")
             yield (astyle.style_default, "%s(" % self.__class__.__name__)
             for part in xrepr(self.expr, "default"):
                 yield part
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "<%s.%s expr=%r at 0x%x>" % \
             (self.__class__.__module__, self.__class__.__name__,
              self.expr, id(self))
 
 
 class ieval(Pipe):
     """
     Evaluate an expression for each object in the input pipe.
 
     Examples::
 
         >>> ils | ieval("_.abspath()")
         # random
         >>> sys.path | ieval(ifile)
         # random
     """
 
     def __init__(self, expr, globals=None, errors="raiseifallfail"):
         """
         Create an ``ieval`` object. ``expr`` can be a callable or a string
         containing an expression. For the meaning of ``globals`` and
         ``errors`` see ``ifilter``.
         """
         self.expr = expr
         self.globals = globals
         self.errors = errors
 
     def __iter__(self):
         if callable(self.expr):
             do = self.expr
         else:
             g = getglobals(self.globals)
             expr = compile(self.expr, "ipipe-expression", "eval")
             def do(item):
                 return eval(expr, g, AttrNamespace(item))
 
         ok = 0
         exc_info = None
         for item in xiter(self.input):
             try:
                 yield do(item)
             except (KeyboardInterrupt, SystemExit):
                 raise
             except Exception, exc:
                 if self.errors == "drop":
                     pass # Ignore errors
                 elif self.errors == "keep":
                     yield item
                 elif self.errors == "keeperror":
                     yield exc
                 elif self.errors == "raise":
                     raise
                 elif self.errors == "raiseifallfail":
                     if exc_info is None:
                         exc_info = sys.exc_info()
         if not ok and exc_info is not None:
             raise exc_info[0], exc_info[1], exc_info[2]
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             input = getattr(self, "input", None)
             if input is not None:
                 for part in xrepr(input, mode):
                     yield part
                 yield (astyle.style_default, " | ")
             yield (astyle.style_default, "%s(" % self.__class__.__name__)
             for part in xrepr(self.expr, "default"):
                 yield part
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "<%s.%s expr=%r at 0x%x>" % \
             (self.__class__.__module__, self.__class__.__name__,
              self.expr, id(self))
 
 
 class ienum(Pipe):
     """
     Enumerate the input pipe (i.e. wrap each input object in an object
     with ``index`` and ``object`` attributes).
 
     Examples::
 
         >>> xrange(20) | ieval("_,_*_") | ienum | ifilter("index % 2 == 0") | ieval("object")
     """
     skip_doctest = True
     
     def __iter__(self):
         fields = ("index", "object")
         for (index, object) in enumerate(xiter(self.input)):
             yield Fields(fields, index=index, object=object)
 
 
 class isort(Pipe):
     """
     Sorts the input pipe.
 
     Examples::
 
         >>> ils | isort("size")
         <IPython.Extensions.ipipe.isort key='size' reverse=False at 0x849ec2c>
         >>> ils | isort("_.isdir(), _.lower()", reverse=True)
         <IPython.Extensions.ipipe.isort key='_.isdir(), _.lower()' reverse=True at 0x849eacc>
         # all-random
     """
 
     def __init__(self, key=None, globals=None, reverse=False):
         """
         Create an ``isort`` object. ``key`` can be a callable or a string
         containing an expression (or ``None`` in which case the items
         themselves will be sorted). If ``reverse`` is true the sort order
         will be reversed. For the meaning of ``globals`` see ``ifilter``.
         """
         self.key = key
         self.globals = globals
         self.reverse = reverse
 
     def __iter__(self):
         if self.key is None:
             items = sorted(xiter(self.input), reverse=self.reverse)
         elif callable(self.key):
             items = sorted(xiter(self.input), key=self.key, reverse=self.reverse)
         else:
             g = getglobals(self.globals)
             key = compile(self.key, "ipipe-expression", "eval")
             def realkey(item):
                 return eval(key, g, AttrNamespace(item))
             items = sorted(xiter(self.input), key=realkey, reverse=self.reverse)
         for item in items:
             yield item
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             input = getattr(self, "input", None)
             if input is not None:
                 for part in xrepr(input, mode):
                     yield part
                 yield (astyle.style_default, " | ")
             yield (astyle.style_default, "%s(" % self.__class__.__name__)
             for part in xrepr(self.key, "default"):
                 yield part
             if self.reverse:
                 yield (astyle.style_default, ", ")
                 for part in xrepr(True, "default"):
                     yield part
             yield (astyle.style_default, ")")
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "<%s.%s key=%r reverse=%r at 0x%x>" % \
             (self.__class__.__module__, self.__class__.__name__,
              self.key, self.reverse, id(self))
 
 
 tab = 3 # for expandtabs()
 
 def _format(field):
     if isinstance(field, str):
         text = repr(field.expandtabs(tab))[1:-1]
     elif isinstance(field, unicode):
         text = repr(field.expandtabs(tab))[2:-1]
     elif isinstance(field, datetime.datetime):
         # Don't use strftime() here, as this requires year >= 1900
         text = "%04d-%02d-%02d %02d:%02d:%02d.%06d" % \
             (field.year, field.month, field.day,
              field.hour, field.minute, field.second, field.microsecond)
     elif isinstance(field, datetime.date):
         text = "%04d-%02d-%02d" % (field.year, field.month, field.day)
     else:
         text = repr(field)
     return text
 
 
 class Display(object):
     class __metaclass__(type):
         def __ror__(self, input):
             return input | self()
 
     def __init__(self, input=None):
         self.input = input
 
     def __ror__(self, input):
         self.input = input
         return self
 
     def display(self):
         pass
 
 
 class iless(Display):
     cmd = "less --quit-if-one-screen --LONG-PROMPT --LINE-NUMBERS --chop-long-lines --shift=8 --RAW-CONTROL-CHARS"
 
     def display(self):
         try:
             pager = os.popen(self.cmd, "w")
             try:
                 for item in xiter(self.input):
                     first = False
                     for attr in xattrs(item, "default"):
                         if first:
                             first = False
                         else:
                             pager.write(" ")
                         attr = upgradexattr(attr)
                         if not isinstance(attr, SelfDescriptor):
                             pager.write(attr.name())
                             pager.write("=")
                         pager.write(str(attr.value(item)))
                     pager.write("\n")
             finally:
                 pager.close()
         except Exception, exc:
             print "%s: %s" % (exc.__class__.__name__, str(exc))
 
 
 class _RedirectIO(object):
     def __init__(self,*args,**kwargs):
         """
         Map the system output streams to self.
         """
         self.stream = StringIO.StringIO()
         self.stdout = sys.stdout
         sys.stdout = self
         self.stderr = sys.stderr
         sys.stderr = self
 
     def write(self, text):
         """
         Write both to screen and to self.
         """
         self.stream.write(text)
         self.stdout.write(text)
         if "\n" in text:
             self.stdout.flush()
 
     def writelines(self, lines):
         """
         Write lines both to screen and to self.
         """
         self.stream.writelines(lines)
         self.stdout.writelines(lines)
         self.stdout.flush()
 
     def restore(self):
         """
         Restore the default system streams.
         """
         self.stdout.flush()
         self.stderr.flush()
         sys.stdout = self.stdout
         sys.stderr = self.stderr
 
 
 class icap(Table):
     """
     Execute a python string and capture any output to stderr/stdout.
 
     Examples::
 
         >>> import time
         >>> icap("for i in range(10): print i, time.sleep(0.1)")
 
     """
     skip_doctest = True
     
     def __init__(self, expr, globals=None):
         self.expr = expr
         self.globals = globals
         log = _RedirectIO()
         try:
             exec(expr, getglobals(globals))
         finally:
             log.restore()
         self.stream = log.stream
 
     def __iter__(self):
         self.stream.seek(0)
         for line in self.stream:
             yield line.rstrip("\r\n")
 
     def __xrepr__(self, mode="default"):
         if mode == "header" or mode == "footer":
             yield (astyle.style_default,
                    "%s(%r)" % (self.__class__.__name__, self.expr))
         else:
             yield (astyle.style_default, repr(self))
 
     def __repr__(self):
         return "%s.%s(%r)" % \
             (self.__class__.__module__, self.__class__.__name__, self.expr)
 
 
 def xformat(value, mode, maxlength):
     align = None
     full = True
     width = 0
     text = astyle.Text()
     for (style, part) in xrepr(value, mode):
         # only consider the first result
         if align is None:
             if isinstance(style, int):
                 # (style, text) really is (alignment, stop)
                 align = style
                 full = part
                 continue
             else:
                 align = -1
                 full = True
         if not isinstance(style, int):
             text.append((style, part))
             width += len(part)
             if width >= maxlength and not full:
                 text.append((astyle.style_ellisis, "..."))
                 width += 3
                 break
     if align is None: # default to left alignment
         align = -1
     return (align, width, text)
 
 
 
 import astyle
 
 class idump(Display):
     # The approximate maximum length of a column entry
     maxattrlength = 200
 
     # Style for column names
     style_header = astyle.Style.fromstr("white:black:bold")
 
     def __init__(self, input=None, *attrs):
         Display.__init__(self, input)
         self.attrs = [upgradexattr(attr) for attr in attrs]
         self.headerpadchar = " "
         self.headersepchar = "|"
         self.datapadchar = " "
         self.datasepchar = "|"
 
     def display(self):
         stream = genutils.Term.cout
         allattrs = []
         attrset = set()
         colwidths = {}
         rows = []
         for item in xiter(self.input):
             row = {}
             attrs = self.attrs
             if not attrs:
                 attrs = xattrs(item, "default")
             for attr in attrs:
                 if attr not in attrset:
                     allattrs.append(attr)
                     attrset.add(attr)
                     colwidths[attr] = len(attr.name())
                 try:
                     value = attr.value(item)
                 except (KeyboardInterrupt, SystemExit):
                     raise
                 except Exception, exc:
                     value = exc
                 (align, width, text) = xformat(value, "cell", self.maxattrlength)
                 colwidths[attr] = max(colwidths[attr], width)
                 # remember alignment, length and colored parts
                 row[attr] = (align, width, text)
             rows.append(row)
 
         stream.write("\n")
         for (i, attr) in enumerate(allattrs):
             attrname = attr.name()
             self.style_header(attrname).write(stream)
             spc = colwidths[attr] - len(attrname)
             if i < len(colwidths)-1:
                 stream.write(self.headerpadchar*spc)
                 stream.write(self.headersepchar)
         stream.write("\n")
 
         for row in rows:
             for (i, attr) in enumerate(allattrs):
                 (align, width, text) = row[attr]
                 spc = colwidths[attr] - width
                 if align == -1:
                     text.write(stream)
                     if i < len(colwidths)-1:
                         stream.write(self.datapadchar*spc)
                 elif align == 0:
                     spc = colwidths[attr] - width
                     spc1 = spc//2
                     spc2 = spc-spc1
                     stream.write(self.datapadchar*spc1)
                     text.write(stream)
                     if i < len(colwidths)-1:
                         stream.write(self.datapadchar*spc2)
                 else:
                     stream.write(self.datapadchar*spc)
                     text.write(stream)
                 if i < len(colwidths)-1:
                     stream.write(self.datasepchar)
             stream.write("\n")
 
 
 class AttributeDetail(Table):
     """
     ``AttributeDetail`` objects are use for displaying a detailed list of object
     attributes.
     """
     def __init__(self, object, descriptor):
         self.object = object
         self.descriptor = descriptor
 
     def __iter__(self):
         return self.descriptor.iter(self.object)
 
     def name(self):
         return self.descriptor.name()
 
     def attrtype(self):
         return self.descriptor.attrtype(self.object)
 
     def valuetype(self):
         return self.descriptor.valuetype(self.object)
 
     def doc(self):
         return self.descriptor.doc(self.object)
 
     def shortdoc(self):
         return self.descriptor.shortdoc(self.object)
 
     def value(self):
         return self.descriptor.value(self.object)
 
     def __xattrs__(self, mode="default"):
         attrs = ("name()", "attrtype()", "valuetype()", "value()", "shortdoc()")
         if mode == "detail":
             attrs += ("doc()",)
         return attrs
 
     def __xrepr__(self, mode="default"):
         yield (-1, True)
         valuetype = self.valuetype()
         if valuetype is not noitem:
             for part in xrepr(valuetype):
                 yield part
             yield (astyle.style_default, " ")
         yield (astyle.style_default, self.attrtype())
         yield (astyle.style_default, " ")
         yield (astyle.style_default, self.name())
         yield (astyle.style_default, " of ")
         for part in xrepr(self.object):
             yield part
 
 
 try:
     from ibrowse import ibrowse
 except ImportError:
     # No curses (probably Windows) => try igrid
     try:
         from igrid import igrid
     except ImportError:
         # no wx either => use ``idump`` as the default display.
         defaultdisplay = idump
     else:
         defaultdisplay = igrid
         __all__.append("igrid")
 else:
     defaultdisplay = ibrowse
     __all__.append("ibrowse")
 
 
 # If we're running under IPython, register our objects with IPython's
 # generic function ``result_display``, else install a displayhook
 # directly as sys.displayhook
 if generics is not None:
     def display_display(obj):
         return obj.display()
     generics.result_display.when_type(Display)(display_display)
 
     def display_tableobject(obj):
         return display_display(defaultdisplay(obj))
     generics.result_display.when_type(Table)(display_tableobject)
 
     def display_tableclass(obj):
         return display_tableobject(obj())
     generics.result_display.when_type(Table.__metaclass__)(display_tableclass)
 else:
     def installdisplayhook():
         _originalhook = sys.displayhook
         def displayhook(obj):
             if isinstance(obj, type) and issubclass(obj, Table):
                 obj = obj()
             if isinstance(obj, Table):
                 obj = defaultdisplay(obj)
             if isinstance(obj, Display):
                 return obj.display()
             else:
                 _originalhook(obj)
         sys.displayhook = displayhook
     installdisplayhook()