pprint — 数据美化打印机 ¶

源代码： Lib/pprint.py

---

The pprint 模块提供可以用作解释器输入形式的 pretty-print (美化打印) 任意 Python 数据结构的能力。若格式化的结构包括非基础 Python 类型的对象，表示可能无法被加载。若是包括文件、套接字或类的对象及许多无法表示成 Python 文字的其它对象，可能属于此情况。

格式化表示将对象保持在一行中若可以的话，和将它们分成多行若不拟合允许宽度。构造 PrettyPrinter 对象明确若需要调节宽度约束。

字典按键排序在计算显示之前。

The pprint 模块定义 1 个类：

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

构造 PrettyPrinter 实例。此构造函数理解几个关键词参数。可以设置输出流使用 stream 关键词；用于流对象的唯一方法是文件协议的 write() 方法。若未指定， PrettyPrinter 采纳 sys.stdout 。为各递归级别添加缩进的数量指定通过 indent ；默认为 1。其它值可能导致输出看起来有点零散，但可以使嵌套更容易被认出。可打印层数的控制通过 depth ；若正打印数据结构太深，下一包含级别将被替换为 ... 。默认情况下，格式化对象的深度不受约束。期望输出宽度的约束使用 width 参数；默认为 80 个字符。若结构无法在约束宽度内被格式化，将尽力而为。若 compact 为 False (默认)，长序列的每项将被格式化成单独行。若 compact 为 True，将拟合尽可能多的项按 width 在每格式化输出行。若 sort_dicts 为 True (默认)，字典将按其键次序被格式化，否则字典将按其键插入次序显示。

3.4 版改变： 添加 compact 参数。

3.8 版改变： 添加 sort_dicts 参数。

>>> 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 模块还提供几个快捷函数：

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

返回格式化表示 object 以字符串形式。 indent , width , depth , compact and sort_dicts 会被传递给 PrettyPrinter 构造函数作为格式化参数。

3.4 版改变： 添加 compact 参数。

3.8 版改变： 添加 sort_dicts 参数。

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

打印格式化表示 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 将被传递给 pprint() as formatting parameters.

3.8 版新增。

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

打印格式化表示 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 , compact and sort_dicts 会被传递给 PrettyPrinter 构造函数作为格式化参数。

3.4 版改变： 添加 compact 参数。

3.8 版改变： 添加 sort_dicts 参数。

>>> 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.

还定义了一个支持函数：

pprint. saferepr ( object ) ¶

返回字符串表示为 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 对象 ¶

PrettyPrinter 实例具有下列方法：

PrettyPrinter. pformat ( object ) ¶

返回格式化表示 object . This takes into account the options passed to the PrettyPrinter 构造函数。

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 参数为 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() 实现。

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.

范例 ¶

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('https://pypi.org/pypi/sampleproject/json') as resp:
...     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 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'}
					

内容表

• pprint — 数据美化打印机
  • PrettyPrinter 对象
  • 范例

上一话题

copy — 浅拷贝和深拷贝操作

下一话题

reprlib — 替代 repr() 实现

本页

• 报告 Bug
• 展示源