
``pprint`` --- Data pretty printer
**********************************

**Source code:** Lib/pprint.py

======================================================================

The ``pprint`` module provides a capability to "pretty-print"
arbitrary Python data structures in a form which can be used as input
to the interpreter. If the formatted structures include objects which
are not fundamental Python types, the representation may not be
loadable.  This may be the case if objects such as files, sockets,
classes, or instances are included, as well as many other built-in
objects which are not representable as Python constants.

The formatted representation keeps objects on a single line if it can,
and breaks them onto multiple lines if they don't fit within the
allowed width. Construct ``PrettyPrinter`` objects explicitly if you
need to adjust the width constraint.

Dictionaries are sorted by key before the display is computed.

The ``pprint`` module defines one class:

class class pprint.PrettyPrinter(indent=1, width=80, depth=None, stream=None)

   Construct a ``PrettyPrinter`` instance.  This constructor
   understands several keyword parameters.  An output stream may be
   set using the *stream* keyword; the only method used on the stream
   object is the file protocol's ``write()`` method.  If not
   specified, the ``PrettyPrinter`` adopts ``sys.stdout``.  Three
   additional parameters may be used to control the formatted
   representation.  The keywords are *indent*, *depth*, and *width*.
   The amount of indentation added for each recursive level is
   specified by *indent*; the default is one.  Other values can cause
   output to look a little odd, but can make nesting easier to spot.
   The number of levels which may be printed is controlled by *depth*;
   if the data structure being printed is too deep, the next contained
   level is replaced by ``...``.  By default, there is no constraint
   on the depth of the objects being formatted.  The desired output
   width is constrained using the *width* parameter; the default is 80
   characters.  If a structure cannot be formatted within the
   constrained width, a best effort will be made.

   >>> import pprint
   >>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']
   >>> stuff.insert(0, stuff[:])
   >>> pp = pprint.PrettyPrinter(indent=4)
   >>> pp.pprint(stuff)
   [   ['spam', 'eggs', 'lumberjack', 'knights', 'ni'],
       'spam',
       'eggs',
       'lumberjack',
       'knights',
       'ni']
   >>> tup = ('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead',
   ... ('parrot', ('fresh fruit',))))))))
   >>> pp = pprint.PrettyPrinter(depth=6)
   >>> pp.pprint(tup)
   ('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead', (...)))))))

The ``PrettyPrinter`` class supports several derivative functions:

pprint.pformat(object, indent=1, width=80, depth=None)

   Return the formatted representation of *object* as a string.
   *indent*, *width* and *depth* will be passed to the
   ``PrettyPrinter`` constructor as formatting parameters.

pprint.pprint(object, stream=None, indent=1, width=80, depth=None)

   Prints the formatted representation of *object* on *stream*,
   followed by a newline.  If *stream* is ``None``, ``sys.stdout`` is
   used.  This may be used in the interactive interpreter instead of
   the ``print()`` function for inspecting values (you can even
   reassign ``print = pprint.pprint`` for use within a scope).
   *indent*, *width* and *depth* will be passed to the
   ``PrettyPrinter`` constructor as formatting parameters.

   >>> import pprint
   >>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni']
   >>> stuff.insert(0, stuff)
   >>> pprint.pprint(stuff)
   [<Recursion on list with id=...>,
    'spam',
    'eggs',
    'lumberjack',
    'knights',
    'ni']

pprint.isreadable(object)

   Determine if the formatted representation of *object* is
   "readable," or can be used to reconstruct the value using
   ``eval()``.  This always returns ``False`` for recursive objects.

   >>> pprint.isreadable(stuff)
   False

pprint.isrecursive(object)

   Determine if *object* requires a recursive representation.

One more support function is also defined:

pprint.saferepr(object)

   Return a string representation of *object*, protected against
   recursive data structures.  If the representation of *object*
   exposes a recursive entry, the recursive reference will be
   represented as ``<Recursion on typename with id=number>``.  The
   representation is not otherwise formatted.

   >>> pprint.saferepr(stuff)
   "[<Recursion on list with id=...>, 'spam', 'eggs', 'lumberjack', 'knights', 'ni']"


PrettyPrinter Objects
=====================

``PrettyPrinter`` instances have the following methods:

PrettyPrinter.pformat(object)

   Return the formatted representation of *object*.  This takes into
   account the options passed to the ``PrettyPrinter`` constructor.

PrettyPrinter.pprint(object)

   Print the formatted representation of *object* on the configured
   stream, followed by a newline.

The following methods provide the implementations for the
corresponding functions of the same names.  Using these methods on an
instance is slightly more efficient since new ``PrettyPrinter``
objects don't need to be created.

PrettyPrinter.isreadable(object)

   Determine if the formatted representation of the object is
   "readable," or can be used to reconstruct the value using
   ``eval()``.  Note that this returns ``False`` for recursive
   objects.  If the *depth* parameter of the ``PrettyPrinter`` is set
   and the object is deeper than allowed, this returns ``False``.

PrettyPrinter.isrecursive(object)

   Determine if the object requires a recursive representation.

This method is provided as a hook to allow subclasses to modify the
way objects are converted to strings.  The default implementation uses
the internals of the ``saferepr()`` implementation.

PrettyPrinter.format(object, context, maxlevels, level)

   Returns three values: the formatted version of *object* as a
   string, a flag indicating whether the result is readable, and a
   flag indicating whether recursion was detected.  The first argument
   is the object to be presented.  The second is a dictionary which
   contains the ``id()`` of objects that are part of the current
   presentation context (direct and indirect containers for *object*
   that are affecting the presentation) as the keys; if an object
   needs to be presented which is already represented in *context*,
   the third return value should be ``True``.  Recursive calls to the
   ``format()`` method should add additional entries for containers to
   this dictionary.  The third argument, *maxlevels*, gives the
   requested limit to recursion; this will be ``0`` if there is no
   requested limit.  This argument should be passed unmodified to
   recursive calls. The fourth argument, *level*, gives the current
   level; recursive calls should be passed a value less than that of
   the current call.


Example
=======

To demonstrate several uses of the ``pprint()`` function and its
parameters, let's fetch information about a project from PyPI:

   >>> import json
   >>> import pprint
   >>> from urllib.request import urlopen
   >>> with urlopen('http://pypi.python.org/pypi/configparser/json') as url:
   ...     http_info = url.info()
   ...     raw_data = url.read().decode(http_info.get_content_charset())
   >>> project_info = json.loads(raw_data)
   >>> result = {'headers': http_info.items(), 'body': project_info}

In its basic form, ``pprint()`` shows the whole object:

   >>> pprint.pprint(result)
   {'body': {'info': {'_pypi_hidden': False,
                      '_pypi_ordering': 12,
                      'classifiers': ['Development Status :: 4 - Beta',
                                      'Intended Audience :: Developers',
                                      'License :: OSI Approved :: MIT License',
                                      'Natural Language :: English',
                                      'Operating System :: OS Independent',
                                      'Programming Language :: Python',
                                      'Programming Language :: Python :: 2',
                                      'Programming Language :: Python :: 2.6',
                                      'Programming Language :: Python :: 2.7',
                                      'Topic :: Software Development :: Libraries',
                                      'Topic :: Software Development :: Libraries :: Python Modules'],
                      'download_url': 'UNKNOWN',
                      'home_page': 'http://docs.python.org/py3k/library/configparser.html',
                      'keywords': 'configparser ini parsing conf cfg configuration file',
                      'license': 'MIT',
                      'name': 'configparser',
                      'package_url': 'http://pypi.python.org/pypi/configparser',
                      'platform': 'any',
                      'release_url': 'http://pypi.python.org/pypi/configparser/3.2.0r3',
                      'requires_python': None,
                      'stable_version': None,
                      'summary': 'This library brings the updated configparser from Python 3.2+ to Python 2.6-2.7.',
                      'version': '3.2.0r3'},
           'urls': [{'comment_text': '',
                     'downloads': 47,
                     'filename': 'configparser-3.2.0r3.tar.gz',
                     'has_sig': False,
                     'md5_digest': '8500fd87c61ac0de328fc996fce69b96',
                     'packagetype': 'sdist',
                     'python_version': 'source',
                     'size': 32281,
                     'upload_time': '2011-05-10T16:28:50',
                     'url': 'http://pypi.python.org/packages/source/c/configparser/configparser-3.2.0r3.tar.gz'}]},
   'headers': [('Date', 'Sat, 14 May 2011 12:48:52 GMT'),
               ('Server', 'Apache/2.2.16 (Debian)'),
               ('Content-Disposition', 'inline'),
               ('Connection', 'close'),
               ('Transfer-Encoding', 'chunked'),
               ('Content-Type', 'application/json; charset="UTF-8"')]}

The result can be limited to a certain *depth* (ellipsis is used for
deeper contents):

   >>> pprint.pprint(result, depth=3)
   {'body': {'info': {'_pypi_hidden': False,
                      '_pypi_ordering': 12,
                      'classifiers': [...],
                      'download_url': 'UNKNOWN',
                      'home_page': 'http://docs.python.org/py3k/library/configparser.html',
                      'keywords': 'configparser ini parsing conf cfg configuration file',
                      'license': 'MIT',
                      'name': 'configparser',
                      'package_url': 'http://pypi.python.org/pypi/configparser',
                      'platform': 'any',
                      'release_url': 'http://pypi.python.org/pypi/configparser/3.2.0r3',
                      'requires_python': None,
                      'stable_version': None,
                      'summary': 'This library brings the updated configparser from Python 3.2+ to Python 2.6-2.7.',
                      'version': '3.2.0r3'},
           'urls': [{...}]},
   'headers': [('Date', 'Sat, 14 May 2011 12:48:52 GMT'),
               ('Server', 'Apache/2.2.16 (Debian)'),
               ('Content-Disposition', 'inline'),
               ('Connection', 'close'),
               ('Transfer-Encoding', 'chunked'),
               ('Content-Type', 'application/json; charset="UTF-8"')]}

Additionally, maximum *width* can be suggested. If a long object
cannot be split, the specified width will be exceeded:

   >>> pprint.pprint(result['headers'], width=30)
   [('Date',
     'Sat, 14 May 2011 12:48:52 GMT'),
    ('Server',
     'Apache/2.2.16 (Debian)'),
    ('Content-Disposition',
     'inline'),
    ('Connection', 'close'),
    ('Transfer-Encoding',
     'chunked'),
    ('Content-Type',
     'application/json; charset="UTF-8"')]
