.. 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:
.. index:: single: ...; placeholder
The :mod:`pprint` module also provides several shortcut functions:
.. function:: pformat(object, indent=1, width=80, depth=None, *, \ compact=False, sort_dicts=True) Return the formatted representation of *object* as a string. *indent*, *width*, *depth*, *compact* and *sort_dicts* will be passed to the :class:`PrettyPrinter` constructor as formatting parameters. .. versionchanged:: 3.4 Added the *compact* parameter. .. versionchanged:: 3.8 Added the *sort_dicts* parameter.
.. function:: pp(object, *args, sort_dicts=False, **kwargs) Prints the formatted representation of *object* followed by a newline. If *sort_dicts* is false (the default), dictionaries will be displayed with their keys in insertion order, otherwise the dict keys will be sorted. *args* and *kwargs* will be passed to :func:`pprint` as formatting parameters. .. versionadded:: 3.8
.. function:: pprint(object, stream=None, indent=1, width=80, depth=None, *, \ compact=False, sort_dicts=True) 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*, *compact* and *sort_dicts* will be passed to the :class:`PrettyPrinter` constructor as formatting parameters. .. versionchanged:: 3.4 Added the *compact* parameter. .. versionchanged:: 3.8 Added the *sort_dicts* 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 :func:`pprint` shows the whole object:
>>> pprint.pprint(project_info)
{'author': 'The Python Packaging Authority',
'author_email': 'pypa-dev@googlegroups.com',
'bugtrack_url': None,
'classifiers': ['Development Status :: 3 - Alpha',
'Intended Audience :: Developers',
'License :: OSI Approved :: MIT License',
'Programming Language :: Python :: 2',
'Programming Language :: Python :: 2.6',
'Programming Language :: Python :: 2.7',
'Programming Language :: Python :: 3',
'Programming Language :: Python :: 3.2',
'Programming Language :: Python :: 3.3',
'Programming Language :: Python :: 3.4',
'Topic :: Software Development :: Build Tools'],
'description': 'A sample Python project\n'
'=======================\n'
'\n'
'This is the description file for the project.\n'
'\n'
'The file should use UTF-8 encoding and be written using '
'ReStructured Text. It\n'
'will be used to generate the project webpage on PyPI, and '
'should be written for\n'
'that purpose.\n'
'\n'
'Typical contents for this file would include an overview of '
'the project, basic\n'
'usage examples, etc. Generally, including the project '
'changelog in here is not\n'
'a good idea, although a simple "What\'s New" section for the '
'most recent version\n'
'may be appropriate.',
'description_content_type': None,
'docs_url': None,
'download_url': 'UNKNOWN',
'downloads': {'last_day': -1, 'last_month': -1, 'last_week': -1},
'home_page': 'https://github.com/pypa/sampleproject',
'keywords': 'sample setuptools development',
'license': 'MIT',
'maintainer': None,
'maintainer_email': None,
'name': 'sampleproject',
'package_url': 'https://pypi.org/project/sampleproject/',
'platform': 'UNKNOWN',
'project_url': 'https://pypi.org/project/sampleproject/',
'project_urls': {'Download': 'UNKNOWN',
'Homepage': 'https://github.com/pypa/sampleproject'},
'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
'requires_dist': None,
'requires_python': None,
'summary': 'A sample Python project',
'version': '1.2.0'}
The result can be limited to a certain depth (ellipsis is used for deeper contents):
>>> pprint.pprint(project_info, depth=1)
{'author': 'The Python Packaging Authority',
'author_email': 'pypa-dev@googlegroups.com',
'bugtrack_url': None,
'classifiers': [...],
'description': 'A sample Python project\n'
'=======================\n'
'\n'
'This is the description file for the project.\n'
'\n'
'The file should use UTF-8 encoding and be written using '
'ReStructured Text. It\n'
'will be used to generate the project webpage on PyPI, and '
'should be written for\n'
'that purpose.\n'
'\n'
'Typical contents for this file would include an overview of '
'the project, basic\n'
'usage examples, etc. Generally, including the project '
'changelog in here is not\n'
'a good idea, although a simple "What\'s New" section for the '
'most recent version\n'
'may be appropriate.',
'description_content_type': None,
'docs_url': None,
'download_url': 'UNKNOWN',
'downloads': {...},
'home_page': 'https://github.com/pypa/sampleproject',
'keywords': 'sample setuptools development',
'license': 'MIT',
'maintainer': None,
'maintainer_email': None,
'name': 'sampleproject',
'package_url': 'https://pypi.org/project/sampleproject/',
'platform': 'UNKNOWN',
'project_url': 'https://pypi.org/project/sampleproject/',
'project_urls': {...},
'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
'requires_dist': None,
'requires_python': None,
'summary': 'A sample Python project',
'version': '1.2.0'}
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=1, width=60)
{'author': 'The Python Packaging Authority',
'author_email': 'pypa-dev@googlegroups.com',
'bugtrack_url': None,
'classifiers': [...],
'description': 'A sample Python project\n'
'=======================\n'
'\n'
'This is the description file for the '
'project.\n'
'\n'
'The file should use UTF-8 encoding and be '
'written using ReStructured Text. It\n'
'will be used to generate the project '
'webpage on PyPI, and should be written '
'for\n'
'that purpose.\n'
'\n'
'Typical contents for this file would '
'include an overview of the project, '
'basic\n'
'usage examples, etc. Generally, including '
'the project changelog in here is not\n'
'a good idea, although a simple "What\'s '
'New" section for the most recent version\n'
'may be appropriate.',
'description_content_type': None,
'docs_url': None,
'download_url': 'UNKNOWN',
'downloads': {...},
'home_page': 'https://github.com/pypa/sampleproject',
'keywords': 'sample setuptools development',
'license': 'MIT',
'maintainer': None,
'maintainer_email': None,
'name': 'sampleproject',
'package_url': 'https://pypi.org/project/sampleproject/',
'platform': 'UNKNOWN',
'project_url': 'https://pypi.org/project/sampleproject/',
'project_urls': {...},
'release_url': 'https://pypi.org/project/sampleproject/1.2.0/',
'requires_dist': None,
'requires_python': None,
'summary': 'A sample Python project',
'version': '1.2.0'}
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