| Python 3.6.5 Documentation > "pprint" — Data pretty printer
"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.
The "pprint" module defines one class:
class pprint.PrettyPrinter(indent=1, width=80, depth=None, stream=None, *, compact=False)
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". 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. If *compact* is
false (the default) each item of a long 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.
Changed in version 3.4: Added the *compact* parameter.
>>> 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', (...)))))))
The "pprint" module also provides several shortcut functions:
pprint.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
"PrettyPrinter" constructor as formatting parameters.
Changed in version 3.4: Added the *compact* parameter.
pprint.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 "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
"PrettyPrinter" constructor as formatting parameters.
Changed in version 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']
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/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, "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': [{...}, {...}]}
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