:mod:`pprint` --- Data pretty printer
.. module:: pprint :synopsis: Data pretty printer.
.. moduleauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
Source code: :source:`Lib/pprint.py`
The :mod:`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 or classes are included, as well as many other objects which are not representable as Python literals.
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 :class:`PrettyPrinter` objects explicitly if you need to adjust the width constraint.
Dictionaries are sorted by key before the display is computed.
The :mod:`pprint` module defines one class:
The :mod:`pprint` module also provides several shortcut functions:
.. function:: pformat(object, indent=1, width=80, depth=None, *, compact=False)
Return the formatted representation of *object* as a string. *indent*,
*width*, *depth* and *compact* will be passed to the :class:`PrettyPrinter`
constructor as formatting parameters.
.. versionchanged:: 3.4
Added the *compact* parameter.
.. function:: pprint(object, stream=None, indent=1, width=80, depth=None, *, \
compact=False)
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 :func:`print` function for
inspecting values (you can even reassign ``print = pprint.pprint`` for use
within a scope). *indent*, *width*, *depth* and *compact* will be passed
to the :class:`PrettyPrinter` constructor as formatting parameters.
.. versionchanged:: 3.4
Added the *compact* parameter.
>>> 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']
.. function:: isreadable(object)
.. index:: builtin: eval
Determine if the formatted representation of *object* is "readable," or can be
used to reconstruct the value using :func:`eval`. This always returns ``False``
for recursive objects.
>>> pprint.isreadable(stuff)
False
.. function:: isrecursive(object) Determine if *object* requires a recursive representation.
One more support function is also defined:
.. function:: 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']"
:class:`PrettyPrinter` instances have the following methods:
.. method:: PrettyPrinter.pformat(object) Return the formatted representation of *object*. This takes into account the options passed to the :class:`PrettyPrinter` constructor.
.. method:: 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 :class:`PrettyPrinter` objects don't need to be created.
.. method:: PrettyPrinter.isreadable(object) .. index:: builtin: eval Determine if the formatted representation of the object is "readable," or can be used to reconstruct the value using :func:`eval`. Note that this returns ``False`` for recursive objects. If the *depth* parameter of the :class:`PrettyPrinter` is set and the object is deeper than allowed, this returns ``False``.
.. method:: 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 :func:`saferepr` implementation.
.. method:: 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 :func:`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 :meth:`.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.
To demonstrate several uses of the :func:`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/Twisted/json') as url:
... http_info = url.info()
... raw_data = url.read().decode(http_info.get_content_charset())
>>> project_info = json.loads(raw_data)
In its basic form, :func:`pprint` shows the whole object:
>>> pprint.pprint(project_info)
{'info': {'_pypi_hidden': False,
'_pypi_ordering': 125,
'author': 'Glyph Lefkowitz',
'author_email': 'glyph@twistedmatrix.com',
'bugtrack_url': '',
'cheesecake_code_kwalitee_id': None,
'cheesecake_documentation_id': None,
'cheesecake_installability_id': None,
'classifiers': ['Programming Language :: Python :: 2.6',
'Programming Language :: Python :: 2.7',
'Programming Language :: Python :: 2 :: Only'],
'description': 'An extensible framework for Python programming, with '
'special focus\r\n'
'on event-based network programming and multiprotocol '
'integration.',
'docs_url': '',
'download_url': 'UNKNOWN',
'home_page': 'http://twistedmatrix.com/',
'keywords': '',
'license': 'MIT',
'maintainer': '',
'maintainer_email': '',
'name': 'Twisted',
'package_url': 'http://pypi.python.org/pypi/Twisted',
'platform': 'UNKNOWN',
'release_url': 'http://pypi.python.org/pypi/Twisted/12.3.0',
'requires_python': None,
'stable_version': None,
'summary': 'An asynchronous networking framework written in Python',
'version': '12.3.0'},
'urls': [{'comment_text': '',
'downloads': 71844,
'filename': 'Twisted-12.3.0.tar.bz2',
'has_sig': False,
'md5_digest': '6e289825f3bf5591cfd670874cc0862d',
'packagetype': 'sdist',
'python_version': 'source',
'size': 2615733,
'upload_time': '2012-12-26T12:47:03',
'url': 'https://pypi.python.org/packages/source/T/Twisted/Twisted-12.3.0.tar.bz2'},
{'comment_text': '',
'downloads': 5224,
'filename': 'Twisted-12.3.0.win32-py2.7.msi',
'has_sig': False,
'md5_digest': '6b778f5201b622a5519a2aca1a2fe512',
'packagetype': 'bdist_msi',
'python_version': '2.7',
'size': 2916352,
'upload_time': '2012-12-26T12:48:15',
'url': 'https://pypi.python.org/packages/2.7/T/Twisted/Twisted-12.3.0.win32-py2.7.msi'}]}
The result can be limited to a certain depth (ellipsis is used for deeper contents):
>>> pprint.pprint(project_info, depth=2)
{'info': {'_pypi_hidden': False,
'_pypi_ordering': 125,
'author': 'Glyph Lefkowitz',
'author_email': 'glyph@twistedmatrix.com',
'bugtrack_url': '',
'cheesecake_code_kwalitee_id': None,
'cheesecake_documentation_id': None,
'cheesecake_installability_id': None,
'classifiers': [...],
'description': 'An extensible framework for Python programming, with '
'special focus\r\n'
'on event-based network programming and multiprotocol '
'integration.',
'docs_url': '',
'download_url': 'UNKNOWN',
'home_page': 'http://twistedmatrix.com/',
'keywords': '',
'license': 'MIT',
'maintainer': '',
'maintainer_email': '',
'name': 'Twisted',
'package_url': 'http://pypi.python.org/pypi/Twisted',
'platform': 'UNKNOWN',
'release_url': 'http://pypi.python.org/pypi/Twisted/12.3.0',
'requires_python': None,
'stable_version': None,
'summary': 'An asynchronous networking framework written in Python',
'version': '12.3.0'},
'urls': [{...}, {...}]}
Additionally, maximum character width can be suggested. If a long object cannot be split, the specified width will be exceeded:
>>> pprint.pprint(project_info, depth=2, width=50)
{'info': {'_pypi_hidden': False,
'_pypi_ordering': 125,
'author': 'Glyph Lefkowitz',
'author_email': 'glyph@twistedmatrix.com',
'bugtrack_url': '',
'cheesecake_code_kwalitee_id': None,
'cheesecake_documentation_id': None,
'cheesecake_installability_id': None,
'classifiers': [...],
'description': 'An extensible '
'framework for Python '
'programming, with '
'special focus\r\n'
'on event-based network '
'programming and '
'multiprotocol '
'integration.',
'docs_url': '',
'download_url': 'UNKNOWN',
'home_page': 'http://twistedmatrix.com/',
'keywords': '',
'license': 'MIT',
'maintainer': '',
'maintainer_email': '',
'name': 'Twisted',
'package_url': 'http://pypi.python.org/pypi/Twisted',
'platform': 'UNKNOWN',
'release_url': 'http://pypi.python.org/pypi/Twisted/12.3.0',
'requires_python': None,
'stable_version': None,
'summary': 'An asynchronous networking '
'framework written in '
'Python',
'version': '12.3.0'},
'urls': [{...}, {...}]}