pprint --- 資料美化列印器¶
原始碼：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, adjustable by the width parameter defaulting to 80 characters.
Dictionaries are sorted by key before the display is computed.
在 3.9 版的變更: Added support for pretty-printing types.SimpleNamespace.
在 3.10 版的變更: Added support for pretty-printing dataclasses.dataclass.
函式¶
- pprint.pp(object, stream=None, indent=1, width=80, depth=None, *, compact=False, sort_dicts=False, underscore_numbers=False)¶
Prints the formatted representation of object, followed by a newline. This function may be used in the interactive interpreter instead of the
print()function for inspecting values. Tip: you can reassignprint = pprint.ppfor use within a scope.- 參數:
object -- The object to be printed.
stream (file-like object | None) -- A file-like object to which the output will be written by calling its
write()method. IfNone(the default),sys.stdoutis used.indent (int) -- The amount of indentation added for each nesting level.
width (int) -- 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.
depth (int | None) -- 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
.... IfNone(the default), there is no constraint on the depth of the objects being formatted.compact (bool) -- Control the way long sequences are formatted. If
False(the default), each item of a sequence will be formatted on a separate line, otherwise as many items as will fit within the width will be formatted on each output line.sort_dicts (bool) -- If
True, dictionaries will be formatted with their keys sorted, otherwise they will be displayed in insertion order (the default).underscore_numbers (bool) -- If
True, integers will be formatted with the_character for a thousands separator, otherwise underscores are not displayed (the default).
>>> 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']
在 3.8 版被加入.
- pprint.pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False, sort_dicts=True, underscore_numbers=False)¶
Alias for
pp()with sort_dicts set toTrueby default, which would automatically sort the dictionaries' keys, you might want to usepp()instead where it isFalseby 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
PrettyPrinterconstructor as formatting parameters and their meanings are as described in the documentation above.
- pprint.isreadable(object)¶
Determine if the formatted representation of object is "readable", or can be used to reconstruct the value using
eval(). This always returnsFalsefor recursive objects.>>> pprint.isreadable(stuff) False
- pprint.isrecursive(object)¶
Determine if object requires a recursive representation. This function is subject to the same limitations as noted in
saferepr()below and may raise anRecursionErrorif it fails to detect a recursive object.
- pprint.saferepr(object)¶
Return a string representation of object, protected against recursion in some common data structures, namely instances of
dict,listandtupleor subclasses whose__repr__has not been overridden. 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 物件¶
- class pprint.PrettyPrinter(indent=1, width=80, depth=None, stream=None, *, compact=False, sort_dicts=True, underscore_numbers=False)¶
Construct a
PrettyPrinterinstance.Arguments have the same meaning as for
pp(). Note that they are in a different order, and that sort_dicts defaults toTrue.>>> 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', (...)))))))
在 3.4 版的變更: 新增 compact 參數。
在 3.8 版的變更: 新增 sort_dicts 參數。
在 3.10 版的變更: 新增 underscore_numbers 參數。
在 3.11 版的變更: No longer attempts to write to
sys.stdoutif it isNone.
PrettyPrinter instances have the following methods:
- PrettyPrinter.pformat(object)¶
Return the formatted representation of object. This takes into account the options passed to the
PrettyPrinterconstructor.
- 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 returnsFalsefor recursive objects. If the depth parameter of thePrettyPrinteris set and the object is deeper than allowed, this returnsFalse.
- 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 beTrue. Recursive calls to theformat()method should add additional entries for containers to this dictionary. The third argument, maxlevels, gives the requested limit to recursion; this will be0if 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.
範例¶
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/1.2.0/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'}