pprint — Data pretty printer — Python 3.11.15 documentation
Description: 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 struc...

# `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 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 `PrettyPrinter` objects explicitly if you need to adjust the width constraint.

Dictionaries are sorted by key before the display is computed.

Changed in version 3.9: Added support for pretty-printing `types.SimpleNamespace`.

Changed in version 3.10: Added support for pretty-printing `dataclasses.dataclass`.

## Functions

pprint.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 `pprint()` as formatting parameters.

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

  New in version 3.8.

pprint.pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True, underscore_numbers=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 `print()` function for inspecting values (you can even reassign `print = pprint.pprint` for use within a scope).

  The configuration parameters stream, indent, width, depth, compact, sort_dicts and underscore_numbers are passed to the `PrettyPrinter` constructor and their meanings are as described in its documentation below.

  Note that sort_dicts is `True` by default and you might want to use `pp()` instead where it is `False` by default.

pprint.pformat(object, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True, underscore_numbers=False)

  Return the formatted representation of object as a string. indent, width, depth, compact, sort_dicts and underscore_numbers are passed to the `PrettyPrinter` constructor as formatting parameters and their meanings are as described in its documentation below.

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.

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

This module defines one class:

class pprint.PrettyPrinter(indent=1, width=80, depth=None, stream=None, *, compact=False, sort_dicts=True, underscore_numbers=False)

  Construct a `PrettyPrinter` instance. This constructor understands several keyword parameters.

  stream (default `sys.stdout`) is a file-like object to which the output will be written by calling its `write()` method. If both stream and `sys.stdout` are `None`, then `pprint()` silently returns.

  Other values configure the manner in which nesting of complex data structures is displayed.

  indent (default 1) specifies the amount of indentation added for each nesting level.

  depth controls the number of nesting levels which may be printed; 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.

  width (default 80) specifies the desired maximum number of characters per line in the output. If a structure cannot be formatted within the width constraint, a best effort will be made.

  compact impacts the way that long sequences (lists, tuples, sets, etc) are formatted. If compact is false (the default) then each item of a sequence will be formatted on a separate line. If compact is true, as many items as will fit within the width will be formatted on each output line.

  If sort_dicts is true (the default), dictionaries will be formatted with their keys sorted, otherwise they will display in insertion order.

  If underscore_numbers is true, integers will be formatted with the `_` character for a thousands separator, otherwise underscores are not displayed (the default).

  Changed in version 3.4: Added the compact parameter.

  Changed in version 3.8: Added the sort_dicts parameter.

  Changed in version 3.10: Added the underscore_numbers parameter.

  Changed in version 3.11: No longer attempts to write to `sys.stdout` if it is `None`.

      >>> 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']
      >>> pp = pprint.PrettyPrinter(width=41, compact=True)
      >>> 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', (...)))))))

`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 `pp()` function and its parameters, let’s fetch information about a project from PyPI:

    >>> import json
    >>> import pprint
    >>> from urllib.request import urlopen
    >>> with urlopen('https://pypi.org/pypi/sampleproject/json') as resp:
    ...     project_info = json.load(resp)['info']

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

    >>> pprint.pp(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.pp(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.pp(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'}