pprint — Data pretty printer

Source code:Lib/pprint.py

Thepprint module provides a capability to “pretty-print” arbitraryPython data structures in a form which can be used as input to the interpreter.If the formatted structures include objects which are not fundamental Pythontypes, the representation may not be loadable. This may be the case if objectssuch as files, sockets or classes are included, as well as many otherobjects which are not representable as Python literals.

The formatted representation keeps objects on a single line if it can, andbreaks them onto multiple lines if they don’t fit within the allowed width.ConstructPrettyPrinter objects explicitly if you need to adjust thewidth constraint.

Dictionaries are sorted by key before the display is computed.

Changed in version 3.9:Added support for pretty-printingtypes.SimpleNamespace.

Thepprint module defines one class:

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

Construct aPrettyPrinter instance. This constructor understandsseveral keyword parameters. An output stream may be set using thestreamkeyword; the only method used on the stream object is the file protocol’swrite() method. If not specified, thePrettyPrinter adoptssys.stdout. Theamount of indentation added for each recursive level is specified byindent;the default is one. Other values can cause output to look a little odd, but canmake nesting easier to spot. The number of levels which may be printed iscontrolled bydepth; if the data structure being printed is too deep, the nextcontained level is replaced by.... By default, there is no constraint onthe depth of the objects being formatted. The desired output width isconstrained using thewidth parameter; the default is 80 characters. If astructure cannot be formatted within the constrained width, a best effort willbe made. Ifcompact is false (the default) each item of a long sequencewill be formatted on a separate line. Ifcompact is true, as many itemsas will fit within thewidth will be formatted on each output line. Ifsort_dicts is true (the default), dictionaries will be formatted with theirkeys sorted, otherwise they will display in insertion order.

Changed in version 3.4:Added thecompact parameter.

Changed in version 3.8:Added thesort_dicts parameter.

>>>importpprint>>>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', (...)))))))

Thepprint module also provides several shortcut functions:

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

Return the formatted representation ofobject as a string.indent,width,depth,compact andsort_dicts will be passed to thePrettyPrinter constructor as formatting parameters.

Changed in version 3.4:Added thecompact parameter.

Changed in version 3.8:Added thesort_dicts parameter.

pprint.pp(object,*args,sort_dicts=False,**kwargs)

Prints the formatted representation ofobject followed by a newline.Ifsort_dicts is false (the default), dictionaries will be displayed withtheir keys in insertion order, otherwise the dict keys will be sorted.args andkwargs will be passed topprint() as formattingparameters.

New in version 3.8.

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

Prints the formatted representation ofobject onstream, followed by anewline. Ifstream isNone,sys.stdout is used. This may be usedin the interactive interpreter instead of theprint() function forinspecting values (you can even reassignprint=pprint.pprint for usewithin a scope).indent,width,depth,compact andsort_dicts willbe passed to thePrettyPrinter constructor as formatting parameters.

Changed in version 3.4:Added thecompact parameter.

Changed in version 3.8:Added thesort_dicts parameter.

>>>importpprint>>>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 ofobject is “readable”, or can beused to reconstruct the value usingeval(). This always returnsFalsefor recursive objects.

>>>pprint.isreadable(stuff)False
pprint.isrecursive(object)

Determine ifobject requires a recursive representation.

One more support function is also defined:

pprint.saferepr(object)

Return a string representation ofobject, protected against recursive datastructures. If the representation ofobject exposes a recursive entry, therecursive reference will be represented as<Recursionontypenamewithid=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 ofobject. This takes into account theoptions passed to thePrettyPrinter constructor.

PrettyPrinter.pprint(object)

Print the formatted representation ofobject on the configured stream,followed by a newline.

The following methods provide the implementations for the correspondingfunctions of the same names. Using these methods on an instance is slightlymore efficient since newPrettyPrinter objects don’t need to becreated.

PrettyPrinter.isreadable(object)

Determine if the formatted representation of the object is “readable,” or can beused to reconstruct the value usingeval(). Note that this returnsFalse for recursive objects. If thedepth parameter of thePrettyPrinter is set and the object is deeper than allowed, thisreturnsFalse.

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 objectsare converted to strings. The default implementation uses the internals of thesaferepr() implementation.

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

Returns three values: the formatted version ofobject as a string, a flagindicating whether the result is readable, and a flag indicating whetherrecursion was detected. The first argument is the object to be presented. Thesecond is a dictionary which contains theid() of objects that are part ofthe current presentation context (direct and indirect containers forobjectthat are affecting the presentation) as the keys; if an object needs to bepresented which is already represented incontext, the third return valueshould beTrue. Recursive calls to theformat() method should addadditional entries for containers to this dictionary. The third argument,maxlevels, gives the requested limit to recursion; this will be0 if thereis no requested limit. This argument should be passed unmodified to recursivecalls. The fourth argument,level, gives the current level; recursive callsshould be passed a value less than that of the current call.

Example

To demonstrate several uses of thepprint() function and its parameters,let’s fetch information about a project fromPyPI:

>>>importjson>>>importpprint>>>fromurllib.requestimporturlopen>>>withurlopen('https://pypi.org/pypi/sampleproject/json')asresp:...project_info=json.load(resp)['info']

In its basic form,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 certaindepth (ellipsis is used for deepercontents):

>>>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 characterwidth can be suggested. If a long objectcannot 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'}