Fix re pattern pretty print (#14559)

Alternative to  #14558

IPython/lib/pretty.py

@@ -1,954 +1,961
 """
 Python advanced pretty printer.  This pretty printer is intended to
 replace the old `pprint` python module which does not allow developers
 to provide their own pretty print callbacks.
 
 This module is based on ruby's `prettyprint.rb` library by `Tanaka Akira`.
 
 
 Example Usage
 -------------
 
 To directly print the representation of an object use `pprint`::
 
     from pretty import pprint
     pprint(complex_object)
 
 To get a string of the output use `pretty`::
 
     from pretty import pretty
     string = pretty(complex_object)
 
 
 Extending
 ---------
 
 The pretty library allows developers to add pretty printing rules for their
 own objects.  This process is straightforward.  All you have to do is to
 add a `_repr_pretty_` method to your object and call the methods on the
 pretty printer passed::
 
     class MyObject(object):
 
         def _repr_pretty_(self, p, cycle):
             ...
 
 Here's an example for a class with a simple constructor::
 
     class MySimpleObject:
 
         def __init__(self, a, b, *, c=None):
             self.a = a
             self.b = b
             self.c = c
 
         def _repr_pretty_(self, p, cycle):
             ctor = CallExpression.factory(self.__class__.__name__)
             if self.c is None:
                 p.pretty(ctor(a, b))
             else:
                 p.pretty(ctor(a, b, c=c))
 
 Here is an example implementation of a `_repr_pretty_` method for a list
 subclass::
 
     class MyList(list):
 
         def _repr_pretty_(self, p, cycle):
             if cycle:
                 p.text('MyList(...)')
             else:
                 with p.group(8, 'MyList([', '])'):
                     for idx, item in enumerate(self):
                         if idx:
                             p.text(',')
                             p.breakable()
                         p.pretty(item)
 
 The `cycle` parameter is `True` if pretty detected a cycle.  You *have* to
 react to that or the result is an infinite loop.  `p.text()` just adds
 non breaking text to the output, `p.breakable()` either adds a whitespace
 or breaks here.  If you pass it an argument it's used instead of the
 default space.  `p.pretty` prettyprints another object using the pretty print
 method.
 
 The first parameter to the `group` function specifies the extra indentation
 of the next line.  In this example the next item will either be on the same
 line (if the items are short enough) or aligned with the right edge of the
 opening bracket of `MyList`.
 
 If you just want to indent something you can use the group function
 without open / close parameters.  You can also use this code::
 
     with p.indent(2):
         ...
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.lib.pretty
    :parts: 3
 
 :copyright: 2007 by Armin Ronacher.
             Portions (c) 2009 by Robert Kern.
 :license: BSD License.
 """
 
 from contextlib import contextmanager
 import datetime
 import os
 import re
 import sys
 import types
 from collections import deque
 from inspect import signature
 from io import StringIO
 from warnings import warn
 
 from IPython.utils.decorators import undoc
 from IPython.utils.py3compat import PYPY
 
 from typing import Dict
 
 __all__ = ['pretty', 'pprint', 'PrettyPrinter', 'RepresentationPrinter',
     'for_type', 'for_type_by_name', 'RawText', 'RawStringLiteral', 'CallExpression']
 
 
 MAX_SEQ_LENGTH = 1000
 _re_pattern_type = type(re.compile(''))
 
 def _safe_getattr(obj, attr, default=None):
     """Safe version of getattr.
 
     Same as getattr, but will return ``default`` on any Exception,
     rather than raising.
     """
     try:
         return getattr(obj, attr, default)
     except Exception:
         return default
 
 @undoc
 class CUnicodeIO(StringIO):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         warn(("CUnicodeIO is deprecated since IPython 6.0. "
               "Please use io.StringIO instead."),
              DeprecationWarning, stacklevel=2)
 
 def _sorted_for_pprint(items):
     """
     Sort the given items for pretty printing. Since some predictable
     sorting is better than no sorting at all, we sort on the string
     representation if normal sorting fails.
     """
     items = list(items)
     try:
         return sorted(items)
     except Exception:
         try:
             return sorted(items, key=str)
         except Exception:
             return items
 
 def pretty(obj, verbose=False, max_width=79, newline='\n', max_seq_length=MAX_SEQ_LENGTH):
     """
     Pretty print the object's representation.
     """
     stream = StringIO()
     printer = RepresentationPrinter(stream, verbose, max_width, newline, max_seq_length=max_seq_length)
     printer.pretty(obj)
     printer.flush()
     return stream.getvalue()
 
 
 def pprint(obj, verbose=False, max_width=79, newline='\n', max_seq_length=MAX_SEQ_LENGTH):
     """
     Like `pretty` but print to stdout.
     """
     printer = RepresentationPrinter(sys.stdout, verbose, max_width, newline, max_seq_length=max_seq_length)
     printer.pretty(obj)
     printer.flush()
     sys.stdout.write(newline)
     sys.stdout.flush()
 
 class _PrettyPrinterBase(object):
 
     @contextmanager
     def indent(self, indent):
         """with statement support for indenting/dedenting."""
         self.indentation += indent
         try:
             yield
         finally:
             self.indentation -= indent
 
     @contextmanager
     def group(self, indent=0, open='', close=''):
         """like begin_group / end_group but for the with statement."""
         self.begin_group(indent, open)
         try:
             yield
         finally:
             self.end_group(indent, close)
 
 class PrettyPrinter(_PrettyPrinterBase):
     """
     Baseclass for the `RepresentationPrinter` prettyprinter that is used to
     generate pretty reprs of objects.  Contrary to the `RepresentationPrinter`
     this printer knows nothing about the default pprinters or the `_repr_pretty_`
     callback method.
     """
 
     def __init__(self, output, max_width=79, newline='\n', max_seq_length=MAX_SEQ_LENGTH):
         self.output = output
         self.max_width = max_width
         self.newline = newline
         self.max_seq_length = max_seq_length
         self.output_width = 0
         self.buffer_width = 0
         self.buffer = deque()
 
         root_group = Group(0)
         self.group_stack = [root_group]
         self.group_queue = GroupQueue(root_group)
         self.indentation = 0
 
     def _break_one_group(self, group):
         while group.breakables:
             x = self.buffer.popleft()
             self.output_width = x.output(self.output, self.output_width)
             self.buffer_width -= x.width
         while self.buffer and isinstance(self.buffer[0], Text):
             x = self.buffer.popleft()
             self.output_width = x.output(self.output, self.output_width)
             self.buffer_width -= x.width
 
     def _break_outer_groups(self):
         while self.max_width < self.output_width + self.buffer_width:
             group = self.group_queue.deq()
             if not group:
                 return
             self._break_one_group(group)
 
     def text(self, obj):
         """Add literal text to the output."""
         width = len(obj)
         if self.buffer:
             text = self.buffer[-1]
             if not isinstance(text, Text):
                 text = Text()
                 self.buffer.append(text)
             text.add(obj, width)
             self.buffer_width += width
             self._break_outer_groups()
         else:
             self.output.write(obj)
             self.output_width += width
 
     def breakable(self, sep=' '):
         """
         Add a breakable separator to the output.  This does not mean that it
         will automatically break here.  If no breaking on this position takes
         place the `sep` is inserted which default to one space.
         """
         width = len(sep)
         group = self.group_stack[-1]
         if group.want_break:
             self.flush()
             self.output.write(self.newline)
             self.output.write(' ' * self.indentation)
             self.output_width = self.indentation
             self.buffer_width = 0
         else:
             self.buffer.append(Breakable(sep, width, self))
             self.buffer_width += width
             self._break_outer_groups()
 
     def break_(self):
         """
         Explicitly insert a newline into the output, maintaining correct indentation.
         """
         group = self.group_queue.deq()
         if group:
             self._break_one_group(group)
         self.flush()
         self.output.write(self.newline)
         self.output.write(' ' * self.indentation)
         self.output_width = self.indentation
         self.buffer_width = 0
 
 
     def begin_group(self, indent=0, open=''):
         """
         Begin a group.
         The first parameter specifies the indentation for the next line (usually
         the width of the opening text), the second the opening text.  All
         parameters are optional.
         """
         if open:
             self.text(open)
         group = Group(self.group_stack[-1].depth + 1)
         self.group_stack.append(group)
         self.group_queue.enq(group)
         self.indentation += indent
 
     def _enumerate(self, seq):
         """like enumerate, but with an upper limit on the number of items"""
         for idx, x in enumerate(seq):
             if self.max_seq_length and idx >= self.max_seq_length:
                 self.text(',')
                 self.breakable()
                 self.text('...')
                 return
             yield idx, x
 
     def end_group(self, dedent=0, close=''):
         """End a group. See `begin_group` for more details."""
         self.indentation -= dedent
         group = self.group_stack.pop()
         if not group.breakables:
             self.group_queue.remove(group)
         if close:
             self.text(close)
 
     def flush(self):
         """Flush data that is left in the buffer."""
         for data in self.buffer:
             self.output_width += data.output(self.output, self.output_width)
         self.buffer.clear()
         self.buffer_width = 0
 
 
 def _get_mro(obj_class):
     """ Get a reasonable method resolution order of a class and its superclasses
     for both old-style and new-style classes.
     """
     if not hasattr(obj_class, '__mro__'):
         # Old-style class. Mix in object to make a fake new-style class.
         try:
             obj_class = type(obj_class.__name__, (obj_class, object), {})
         except TypeError:
             # Old-style extension type that does not descend from object.
             # FIXME: try to construct a more thorough MRO.
             mro = [obj_class]
         else:
             mro = obj_class.__mro__[1:-1]
     else:
         mro = obj_class.__mro__
     return mro
 
 
 class RepresentationPrinter(PrettyPrinter):
     """
     Special pretty printer that has a `pretty` method that calls the pretty
     printer for a python object.
 
     This class stores processing data on `self` so you must *never* use
     this class in a threaded environment.  Always lock it or reinstanciate
     it.
 
     Instances also have a verbose flag callbacks can access to control their
     output.  For example the default instance repr prints all attributes and
     methods that are not prefixed by an underscore if the printer is in
     verbose mode.
     """
 
     def __init__(self, output, verbose=False, max_width=79, newline='\n',
         singleton_pprinters=None, type_pprinters=None, deferred_pprinters=None,
         max_seq_length=MAX_SEQ_LENGTH):
 
         PrettyPrinter.__init__(self, output, max_width, newline, max_seq_length=max_seq_length)
         self.verbose = verbose
         self.stack = []
         if singleton_pprinters is None:
             singleton_pprinters = _singleton_pprinters.copy()
         self.singleton_pprinters = singleton_pprinters
         if type_pprinters is None:
             type_pprinters = _type_pprinters.copy()
         self.type_pprinters = type_pprinters
         if deferred_pprinters is None:
             deferred_pprinters = _deferred_type_pprinters.copy()
         self.deferred_pprinters = deferred_pprinters
 
     def pretty(self, obj):
         """Pretty print the given object."""
         obj_id = id(obj)
         cycle = obj_id in self.stack
         self.stack.append(obj_id)
         self.begin_group()
         try:
             obj_class = _safe_getattr(obj, '__class__', None) or type(obj)
             # First try to find registered singleton printers for the type.
             try:
                 printer = self.singleton_pprinters[obj_id]
             except (TypeError, KeyError):
                 pass
             else:
                 return printer(obj, self, cycle)
             # Next walk the mro and check for either:
             #   1) a registered printer
             #   2) a _repr_pretty_ method
             for cls in _get_mro(obj_class):
                 if cls in self.type_pprinters:
                     # printer registered in self.type_pprinters
                     return self.type_pprinters[cls](obj, self, cycle)
                 else:
                     # deferred printer
                     printer = self._in_deferred_types(cls)
                     if printer is not None:
                         return printer(obj, self, cycle)
                     else:
                         # Finally look for special method names.
                         # Some objects automatically create any requested
                         # attribute. Try to ignore most of them by checking for
                         # callability.
                         if '_repr_pretty_' in cls.__dict__:
                             meth = cls._repr_pretty_
                             if callable(meth):
                                 return meth(obj, self, cycle)
                         if (
                             cls is not object
                             # check if cls defines __repr__
                             and "__repr__" in cls.__dict__
                             # check if __repr__ is callable.
                             # Note: we need to test getattr(cls, '__repr__')
                             #   instead of cls.__dict__['__repr__']
                             #   in order to work with descriptors like partialmethod,
                             and callable(_safe_getattr(cls, "__repr__", None))
                         ):
                             return _repr_pprint(obj, self, cycle)
 
             return _default_pprint(obj, self, cycle)
         finally:
             self.end_group()
             self.stack.pop()
 
     def _in_deferred_types(self, cls):
         """
         Check if the given class is specified in the deferred type registry.
 
         Returns the printer from the registry if it exists, and None if the
         class is not in the registry. Successful matches will be moved to the
         regular type registry for future use.
         """
         mod = _safe_getattr(cls, '__module__', None)
         name = _safe_getattr(cls, '__name__', None)
         key = (mod, name)
         printer = None
         if key in self.deferred_pprinters:
             # Move the printer over to the regular registry.
             printer = self.deferred_pprinters.pop(key)
             self.type_pprinters[cls] = printer
         return printer
 
 
 class Printable(object):
 
     def output(self, stream, output_width):
         return output_width
 
 
 class Text(Printable):
 
     def __init__(self):
         self.objs = []
         self.width = 0
 
     def output(self, stream, output_width):
         for obj in self.objs:
             stream.write(obj)
         return output_width + self.width
 
     def add(self, obj, width):
         self.objs.append(obj)
         self.width += width
 
 
 class Breakable(Printable):
 
     def __init__(self, seq, width, pretty):
         self.obj = seq
         self.width = width
         self.pretty = pretty
         self.indentation = pretty.indentation
         self.group = pretty.group_stack[-1]
         self.group.breakables.append(self)
 
     def output(self, stream, output_width):
         self.group.breakables.popleft()
         if self.group.want_break:
             stream.write(self.pretty.newline)
             stream.write(' ' * self.indentation)
             return self.indentation
         if not self.group.breakables:
             self.pretty.group_queue.remove(self.group)
         stream.write(self.obj)
         return output_width + self.width
 
 
 class Group(Printable):
 
     def __init__(self, depth):
         self.depth = depth
         self.breakables = deque()
         self.want_break = False
 
 
 class GroupQueue(object):
 
     def __init__(self, *groups):
         self.queue = []
         for group in groups:
             self.enq(group)
 
     def enq(self, group):
         depth = group.depth
         while depth > len(self.queue) - 1:
             self.queue.append([])
         self.queue[depth].append(group)
 
     def deq(self):
         for stack in self.queue:
             for idx, group in enumerate(reversed(stack)):
                 if group.breakables:
                     del stack[idx]
                     group.want_break = True
                     return group
             for group in stack:
                 group.want_break = True
             del stack[:]
 
     def remove(self, group):
         try:
             self.queue[group.depth].remove(group)
         except ValueError:
             pass
 
 
 class RawText:
     """ Object such that ``p.pretty(RawText(value))`` is the same as ``p.text(value)``.
 
     An example usage of this would be to show a list as binary numbers, using
     ``p.pretty([RawText(bin(i)) for i in integers])``.
     """
     def __init__(self, value):
         self.value = value
 
     def _repr_pretty_(self, p, cycle):
         p.text(self.value)
 
 
 class CallExpression:
     """ Object which emits a line-wrapped call expression in the form `__name(*args, **kwargs)` """
     def __init__(__self, __name, *args, **kwargs):
         # dunders are to avoid clashes with kwargs, as python's name managing
         # will kick in.
         self = __self
         self.name = __name
         self.args = args
         self.kwargs = kwargs
 
     @classmethod
     def factory(cls, name):
         def inner(*args, **kwargs):
             return cls(name, *args, **kwargs)
         return inner
 
     def _repr_pretty_(self, p, cycle):
         # dunders are to avoid clashes with kwargs, as python's name managing
         # will kick in.
 
         started = False
         def new_item():
             nonlocal started
             if started:
                 p.text(",")
                 p.breakable()
             started = True
 
         prefix = self.name + "("
         with p.group(len(prefix), prefix, ")"):
             for arg in self.args:
                 new_item()
                 p.pretty(arg)
             for arg_name, arg in self.kwargs.items():
                 new_item()
                 arg_prefix = arg_name + "="
                 with p.group(len(arg_prefix), arg_prefix):
                     p.pretty(arg)
 
 
 class RawStringLiteral:
     """ Wrapper that shows a string with a `r` prefix """
     def __init__(self, value):
         self.value = value
 
     def _repr_pretty_(self, p, cycle):
         base_repr = repr(self.value)
         if base_repr[:1] in 'uU':
             base_repr = base_repr[1:]
             prefix = 'ur'
         else:
             prefix = 'r'
         base_repr = prefix + base_repr.replace('\\\\', '\\')
         p.text(base_repr)
 
 
 def _default_pprint(obj, p, cycle):
     """
     The default print function.  Used if an object does not provide one and
     it's none of the builtin objects.
     """
     klass = _safe_getattr(obj, '__class__', None) or type(obj)
     if _safe_getattr(klass, '__repr__', None) is not object.__repr__:
         # A user-provided repr. Find newlines and replace them with p.break_()
         _repr_pprint(obj, p, cycle)
         return
     p.begin_group(1, '<')
     p.pretty(klass)
     p.text(' at 0x%x' % id(obj))
     if cycle:
         p.text(' ...')
     elif p.verbose:
         first = True
         for key in dir(obj):
             if not key.startswith('_'):
                 try:
                     value = getattr(obj, key)
                 except AttributeError:
                     continue
                 if isinstance(value, types.MethodType):
                     continue
                 if not first:
                     p.text(',')
                 p.breakable()
                 p.text(key)
                 p.text('=')
                 step = len(key) + 1
                 p.indentation += step
                 p.pretty(value)
                 p.indentation -= step
                 first = False
     p.end_group(1, '>')
 
 
 def _seq_pprinter_factory(start, end):
     """
     Factory that returns a pprint function useful for sequences.  Used by
     the default pprint for tuples and lists.
     """
     def inner(obj, p, cycle):
         if cycle:
             return p.text(start + '...' + end)
         step = len(start)
         p.begin_group(step, start)
         for idx, x in p._enumerate(obj):
             if idx:
                 p.text(',')
                 p.breakable()
             p.pretty(x)
         if len(obj) == 1 and isinstance(obj, tuple):
             # Special case for 1-item tuples.
             p.text(',')
         p.end_group(step, end)
     return inner
 
 
 def _set_pprinter_factory(start, end):
     """
     Factory that returns a pprint function useful for sets and frozensets.
     """
     def inner(obj, p, cycle):
         if cycle:
             return p.text(start + '...' + end)
         if len(obj) == 0:
             # Special case.
             p.text(type(obj).__name__ + '()')
         else:
             step = len(start)
             p.begin_group(step, start)
             # Like dictionary keys, we will try to sort the items if there aren't too many
             if not (p.max_seq_length and len(obj) >= p.max_seq_length):
                 items = _sorted_for_pprint(obj)
             else:
                 items = obj
             for idx, x in p._enumerate(items):
                 if idx:
                     p.text(',')
                     p.breakable()
                 p.pretty(x)
             p.end_group(step, end)
     return inner
 
 
 def _dict_pprinter_factory(start, end):
     """
     Factory that returns a pprint function used by the default pprint of
     dicts and dict proxies.
     """
     def inner(obj, p, cycle):
         if cycle:
             return p.text('{...}')
         step = len(start)
         p.begin_group(step, start)
         keys = obj.keys()
         for idx, key in p._enumerate(keys):
             if idx:
                 p.text(',')
                 p.breakable()
             p.pretty(key)
             p.text(': ')
             p.pretty(obj[key])
         p.end_group(step, end)
     return inner
 
 
 def _super_pprint(obj, p, cycle):
     """The pprint for the super type."""
     p.begin_group(8, '<super: ')
     p.pretty(obj.__thisclass__)
     p.text(',')
     p.breakable()
     if PYPY: # In PyPy, super() objects don't have __self__ attributes
         dself = obj.__repr__.__self__
         p.pretty(None if dself is obj else dself)
     else:
         p.pretty(obj.__self__)
     p.end_group(8, '>')
 
 
 
 class _ReFlags:
     def __init__(self, value):
         self.value = value
 
     def _repr_pretty_(self, p, cycle):
         done_one = False
-        for flag in ('TEMPLATE', 'IGNORECASE', 'LOCALE', 'MULTILINE', 'DOTALL',
-            'UNICODE', 'VERBOSE', 'DEBUG'):
+        for flag in (
+            "IGNORECASE",
+            "LOCALE",
+            "MULTILINE",
+            "DOTALL",
+            "UNICODE",
+            "VERBOSE",
+            "DEBUG",
+        ):
             if self.value & getattr(re, flag):
                 if done_one:
                     p.text('|')
                 p.text('re.' + flag)
                 done_one = True
 
 
 def _re_pattern_pprint(obj, p, cycle):
     """The pprint function for regular expression patterns."""
     re_compile = CallExpression.factory('re.compile')
     if obj.flags:
         p.pretty(re_compile(RawStringLiteral(obj.pattern), _ReFlags(obj.flags)))
     else:
         p.pretty(re_compile(RawStringLiteral(obj.pattern)))
 
 
 def _types_simplenamespace_pprint(obj, p, cycle):
     """The pprint function for types.SimpleNamespace."""
     namespace = CallExpression.factory('namespace')
     if cycle:
         p.pretty(namespace(RawText("...")))
     else:
         p.pretty(namespace(**obj.__dict__))
 
 
 def _type_pprint(obj, p, cycle):
     """The pprint for classes and types."""
     # Heap allocated types might not have the module attribute,
     # and others may set it to None.
 
     # Checks for a __repr__ override in the metaclass. Can't compare the
     # type(obj).__repr__ directly because in PyPy the representation function
     # inherited from type isn't the same type.__repr__
     if [m for m in _get_mro(type(obj)) if "__repr__" in vars(m)][:1] != [type]:
         _repr_pprint(obj, p, cycle)
         return
 
     mod = _safe_getattr(obj, '__module__', None)
     try:
         name = obj.__qualname__
         if not isinstance(name, str):
             # This can happen if the type implements __qualname__ as a property
             # or other descriptor in Python 2.
             raise Exception("Try __name__")
     except Exception:
         name = obj.__name__
         if not isinstance(name, str):
             name = '<unknown type>'
 
     if mod in (None, '__builtin__', 'builtins', 'exceptions'):
         p.text(name)
     else:
         p.text(mod + '.' + name)
 
 
 def _repr_pprint(obj, p, cycle):
     """A pprint that just redirects to the normal repr function."""
     # Find newlines and replace them with p.break_()
     output = repr(obj)
     lines = output.splitlines()
     with p.group():
         for idx, output_line in enumerate(lines):
             if idx:
                 p.break_()
             p.text(output_line)
 
 
 def _function_pprint(obj, p, cycle):
     """Base pprint for all functions and builtin functions."""
     name = _safe_getattr(obj, '__qualname__', obj.__name__)
     mod = obj.__module__
     if mod and mod not in ('__builtin__', 'builtins', 'exceptions'):
         name = mod + '.' + name
     try:
        func_def = name + str(signature(obj))
     except ValueError:
        func_def = name
     p.text('<function %s>' % func_def)
 
 
 def _exception_pprint(obj, p, cycle):
     """Base pprint for all exceptions."""
     name = getattr(obj.__class__, '__qualname__', obj.__class__.__name__)
     if obj.__class__.__module__ not in ('exceptions', 'builtins'):
         name = '%s.%s' % (obj.__class__.__module__, name)
 
     p.pretty(CallExpression(name, *getattr(obj, 'args', ())))
 
 
 #: the exception base
 _exception_base: type
 try:
     _exception_base = BaseException
 except NameError:
     _exception_base = Exception
 
 
 #: printers for builtin types
 _type_pprinters = {
     int:                        _repr_pprint,
     float:                      _repr_pprint,
     str:                        _repr_pprint,
     tuple:                      _seq_pprinter_factory('(', ')'),
     list:                       _seq_pprinter_factory('[', ']'),
     dict:                       _dict_pprinter_factory('{', '}'),
     set:                        _set_pprinter_factory('{', '}'),
     frozenset:                  _set_pprinter_factory('frozenset({', '})'),
     super:                      _super_pprint,
     _re_pattern_type:           _re_pattern_pprint,
     type:                       _type_pprint,
     types.FunctionType:         _function_pprint,
     types.BuiltinFunctionType:  _function_pprint,
     types.MethodType:           _repr_pprint,
     types.SimpleNamespace:      _types_simplenamespace_pprint,
     datetime.datetime:          _repr_pprint,
     datetime.timedelta:         _repr_pprint,
     _exception_base:            _exception_pprint
 }
 
 # render os.environ like a dict
 _env_type = type(os.environ)
 # future-proof in case os.environ becomes a plain dict?
 if _env_type is not dict:
     _type_pprinters[_env_type] = _dict_pprinter_factory('environ{', '}')
 
 _type_pprinters[types.MappingProxyType] = _dict_pprinter_factory("mappingproxy({", "})")
 _type_pprinters[slice] = _repr_pprint
 
 _type_pprinters[range] = _repr_pprint
 _type_pprinters[bytes] = _repr_pprint
 
 #: printers for types specified by name
 _deferred_type_pprinters: Dict = {}
 
 
 def for_type(typ, func):
     """
     Add a pretty printer for a given type.
     """
     oldfunc = _type_pprinters.get(typ, None)
     if func is not None:
         # To support easy restoration of old pprinters, we need to ignore Nones.
         _type_pprinters[typ] = func
     return oldfunc
 
 def for_type_by_name(type_module, type_name, func):
     """
     Add a pretty printer for a type specified by the module and name of a type
     rather than the type object itself.
     """
     key = (type_module, type_name)
     oldfunc = _deferred_type_pprinters.get(key, None)
     if func is not None:
         # To support easy restoration of old pprinters, we need to ignore Nones.
         _deferred_type_pprinters[key] = func
     return oldfunc
 
 
 #: printers for the default singletons
 _singleton_pprinters = dict.fromkeys(map(id, [None, True, False, Ellipsis,
                                       NotImplemented]), _repr_pprint)
 
 
 def _defaultdict_pprint(obj, p, cycle):
     cls_ctor = CallExpression.factory(obj.__class__.__name__)
     if cycle:
         p.pretty(cls_ctor(RawText("...")))
     else:
         p.pretty(cls_ctor(obj.default_factory, dict(obj)))
 
 def _ordereddict_pprint(obj, p, cycle):
     cls_ctor = CallExpression.factory(obj.__class__.__name__)
     if cycle:
         p.pretty(cls_ctor(RawText("...")))
     elif len(obj):
         p.pretty(cls_ctor(list(obj.items())))
     else:
         p.pretty(cls_ctor())
 
 def _deque_pprint(obj, p, cycle):
     cls_ctor = CallExpression.factory(obj.__class__.__name__)
     if cycle:
         p.pretty(cls_ctor(RawText("...")))
     elif obj.maxlen is not None:
         p.pretty(cls_ctor(list(obj), maxlen=obj.maxlen))
     else:
         p.pretty(cls_ctor(list(obj)))
 
 def _counter_pprint(obj, p, cycle):
     cls_ctor = CallExpression.factory(obj.__class__.__name__)
     if cycle:
         p.pretty(cls_ctor(RawText("...")))
     elif len(obj):
         p.pretty(cls_ctor(dict(obj.most_common())))
     else:
         p.pretty(cls_ctor())
 
 
 def _userlist_pprint(obj, p, cycle):
     cls_ctor = CallExpression.factory(obj.__class__.__name__)
     if cycle:
         p.pretty(cls_ctor(RawText("...")))
     else:
         p.pretty(cls_ctor(obj.data))
 
 
 for_type_by_name('collections', 'defaultdict', _defaultdict_pprint)
 for_type_by_name('collections', 'OrderedDict', _ordereddict_pprint)
 for_type_by_name('collections', 'deque', _deque_pprint)
 for_type_by_name('collections', 'Counter', _counter_pprint)
 for_type_by_name("collections", "UserList", _userlist_pprint)
 
 if __name__ == '__main__':
     from random import randrange
     class Foo(object):
         def __init__(self):
             self.foo = 1
             self.bar = re.compile(r'\s+')
             self.blub = dict.fromkeys(range(30), randrange(1, 40))
             self.hehe = 23424.234234
             self.list = ["blub", "blah", self]
 
         def get_foo(self):
             print("foo")
 
     pprint(Foo(), verbose=True)