IPython/lib/pretty.py

# -*- coding: utf-8 -*-
"""
    pretty
    ~~

    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 `__pretty__` method to your object and call the methods on the
    pretty printer passed::

        class MyObject(object):

            def __pretty__(self, p, cycle):
                ...

    Depending on the python version you want to support you have two
    possibilities.  The following list shows the python 2.5 version and the
    compatibility one.


    Here the example implementation of a `__pretty__` method for a list
    subclass for python 2.5 and higher (python 2.5 requires the with statement
    __future__ import)::

        class MyList(list):

            def __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 not
    breaked (if the items are short enough) or aligned with the right edge of
    the opening bracked of `MyList`.

    If you want to support python 2.4 and lower you can use this code::

        class MyList(list):

            def __pretty__(self, p, cycle):
                if cycle:
                    p.text('MyList(...)')
                else:
                    p.begin_group(8, 'MyList([')
                    for idx, item in enumerate(self):
                        if idx:
                            p.text(',')
                            p.breakable()
                        p.pretty(item)
                    p.end_group(8, '])')

    If you just want to indent something you can use the group function
    without open / close parameters.  Under python 2.5 you can also use this
    code::

        with p.indent(2):
            ...

    Or under python2.4 you might want to modify ``p.indentation`` by hand but
    this is rather ugly.

    :copyright: 2007 by Armin Ronacher.
                Portions (c) 2009 by Robert Kern.
    :license: BSD License.
"""
from __future__ import with_statement
from contextlib import contextmanager
import sys
import types
import re
import datetime
from StringIO import StringIO
from collections import deque


__all__ = ['pretty', 'pprint', 'PrettyPrinter', 'RepresentationPrinter',
    'for_type', 'for_type_by_name']


_re_pattern_type = type(re.compile(''))


def pretty(obj, verbose=False, max_width=79, newline='\n'):
    """
    Pretty print the object's representation.
    """
    stream = StringIO()
    printer = RepresentationPrinter(stream, verbose, max_width, newline)
    printer.pretty(obj)
    printer.flush()
    return stream.getvalue()


def pprint(obj, verbose=False, max_width=79, newline='\n'):
    """
    Like `pretty` but print to stdout.
    """
    printer = RepresentationPrinter(sys.stdout, verbose, max_width, newline)
    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:
            with self.indent(indent):
                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 `__pretty__`
    callback method.
    """

    def __init__(self, output, max_width=79, newline='\n'):
        self.output = output
        self.max_width = max_width
        self.newline = newline
        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_outer_groups(self):
        while self.max_width < self.output_width + self.buffer_width:
            group = self.group_queue.deq()
            if not group:
                return
            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 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 begin_group(self, indent=0, open=''):
        """
        Begin a group.  If you want support for python < 2.5 which doesn't has
        the with statement this is the preferred way:

            p.begin_group(1, '{')
            ...
            p.end_group(1, '}')

        The python 2.5 expression would be this:

            with p.group(1, '{', '}'):
                ...

        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 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):

        PrettyPrinter.__init__(self, output, max_width, newline)
        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 = getattr(obj, '__class__', None) or type(obj)
            if hasattr(obj_class, '__pretty__'):
                return obj_class.__pretty__(obj, self, cycle)
            try:
                printer = self.singleton_pprinters[obj_id]
            except (TypeError, KeyError):
                pass
            else:
                return printer(obj, self, cycle)
            for cls in _get_mro(obj_class):
                if cls in self.type_pprinters:
                    return self.type_pprinters[cls](obj, self, cycle)
                else:
                    printer = self._in_deferred_types(cls)
                    if printer is not None:
                        return printer(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 = getattr(cls, '__module__', None)
        name = 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


_baseclass_reprs = (object.__repr__, types.InstanceType.__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 = getattr(obj, '__class__', None) or type(obj)
    if getattr(klass, '__repr__', None) not in _baseclass_reprs:
        # A user-provided repr.
        p.text(repr(obj))
        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, dicts, lists, sets and frozensets.
    """
    def inner(obj, p, cycle):
        if cycle:
            return p.text(start + '...' + end)
        step = len(start)
        p.begin_group(step, start)
        for idx, x in enumerate(obj):
            if idx:
                p.text(',')
                p.breakable()
            p.pretty(x)
        if len(obj) == 1 and type(obj) is tuple:
            # Special case for 1-item tuples.
            p.text(',')
        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('{...}')
        p.begin_group(1, start)
        keys = obj.keys()
        try:
            keys.sort()
        except Exception, e:
            # Sometimes the keys don't sort.
            pass
        for idx, key in enumerate(keys):
            if idx:
                p.text(',')
                p.breakable()
            p.pretty(key)
            p.text(': ')
            p.pretty(obj[key])
        p.end_group(1, end)
    return inner


def _super_pprint(obj, p, cycle):
    """The pprint for the super type."""
    p.begin_group(8, '<super: ')
    p.pretty(obj.__self_class__)
    p.text(',')
    p.breakable()
    p.pretty(obj.__self__)
    p.end_group(8, '>')


def _re_pattern_pprint(obj, p, cycle):
    """The pprint function for regular expression patterns."""
    p.text('re.compile(')
    pattern = repr(obj.pattern)
    if pattern[:1] in 'uU':
        pattern = pattern[1:]
        prefix = 'ur'
    else:
        prefix = 'r'
    pattern = prefix + pattern.replace('\\\\', '\\')
    p.text(pattern)
    if obj.flags:
        p.text(',')
        p.breakable()
        done_one = False
        for flag in ('TEMPLATE', 'IGNORECASE', 'LOCALE', 'MULTILINE', 'DOTALL',
            'UNICODE', 'VERBOSE', 'DEBUG'):
            if obj.flags & getattr(re, flag):
                if done_one:
                    p.text('|')
                p.text('re.' + flag)
                done_one = True
    p.text(')')


def _type_pprint(obj, p, cycle):
    """The pprint for classes and types."""
    if obj.__module__ in ('__builtin__', 'exceptions'):
        name = obj.__name__
    else:
        name = obj.__module__ + '.' + obj.__name__
    p.text(name)


def _repr_pprint(obj, p, cycle):
    """A pprint that just redirects to the normal repr function."""
    p.text(repr(obj))


def _function_pprint(obj, p, cycle):
    """Base pprint for all functions and builtin functions."""
    if obj.__module__ in ('__builtin__', 'exceptions') or not obj.__module__:
        name = obj.__name__
    else:
        name = obj.__module__ + '.' + obj.__name__
    p.text('<function %s>' % name)


def _exception_pprint(obj, p, cycle):
    """Base pprint for all exceptions."""
    if obj.__class__.__module__ == 'exceptions':
        name = obj.__class__.__name__
    else:
        name = '%s.%s' % (
            obj.__class__.__module__,
            obj.__class__.__name__
        )
    step = len(name) + 1
    p.begin_group(step, '(')
    for idx, arg in enumerate(getattr(obj, 'args', ())):
        if idx:
            p.text(',')
            p.breakable()
        p.pretty(arg)
    p.end_group(step, ')')


#: the exception base
try:
    _exception_base = BaseException
except NameError:
    _exception_base = Exception


#: printers for builtin types
_type_pprinters = {
    int:                        _repr_pprint,
    long:                       _repr_pprint,
    float:                      _repr_pprint,
    str:                        _repr_pprint,
    unicode:                    _repr_pprint,
    tuple:                      _seq_pprinter_factory('(', ')'),
    list:                       _seq_pprinter_factory('[', ']'),
    dict:                       _dict_pprinter_factory('{', '}'),
    types.DictProxyType:        _dict_pprinter_factory('<dictproxy {', '}>'),
    set:                        _seq_pprinter_factory('set([', '])'),
    frozenset:                  _seq_pprinter_factory('frozenset([', '])'),
    super:                      _super_pprint,
    _re_pattern_type:           _re_pattern_pprint,
    type:                       _type_pprint,
    types.ClassType:            _type_pprint,
    types.FunctionType:         _function_pprint,
    types.BuiltinFunctionType:  _function_pprint,
    types.SliceType:            _repr_pprint,
    types.MethodType:           _repr_pprint,
    xrange:                     _repr_pprint,
    datetime.datetime:          _repr_pprint,
    datetime.timedelta:         _repr_pprint,
    _exception_base:            _exception_pprint
}

#: printers for types specified by name
_deferred_type_pprinters = {
}

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)


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)