`pprint` --- 數(shù)據(jù)美化輸出?

源代碼： Lib/pprint.py

pprint 模塊提供了“美化打印”任意 Python 數(shù)據(jù)結(jié)構(gòu)的功能，這種美化形式可用作對(duì)解釋器的輸入。如果經(jīng)格式化的結(jié)構(gòu)包含非基本 Python 類型的對(duì)象，則其美化形式可能無(wú)法被加載。包含文件、套接字或類對(duì)象，以及許多其他不能用 Python 字面值來(lái)表示的對(duì)象都有可能導(dǎo)致這樣的結(jié)果。

格式化后的形式會(huì)在可能的情況下以單行來(lái)表示對(duì)象，并在無(wú)法在允許寬度內(nèi)容納對(duì)象的情況下將其分為多行。如果你需要調(diào)整寬度限制則應(yīng)顯式地構(gòu)造 PrettyPrinter 對(duì)象。

字典在計(jì)算其顯示形式前會(huì)先根據(jù)鍵來(lái)排序。

在 3.9 版更改: 添加了對(duì)美化打印 types.SimpleNamespace 的支持。

在 3.10 版更改: 添加了對(duì)美化打印 dataclasses.dataclass 的支持。

pprint 模塊定義了一個(gè)類：

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

構(gòu)造一個(gè) PrettyPrinter 實(shí)例。這個(gè)構(gòu)造器支持一些關(guān)鍵字形參。

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.

其他值可用來(lái)配置復(fù)雜數(shù)據(jù)結(jié)構(gòu)嵌套要以何種形式被展示。

indent (默認(rèn)為 1) 指定要為每個(gè)縮進(jìn)層級(jí)添加的縮進(jìn)量。

depth 控制可被打印的縮進(jìn)層級(jí)數(shù)量；如果要打印的數(shù)據(jù)結(jié)構(gòu)層級(jí)過(guò)深，則其所包含的下一層級(jí)將用 ... 替換。默認(rèn)情況下，對(duì)于被格式化對(duì)象的層級(jí)深度沒(méi)有任何限制。

width (默認(rèn)為 80) 指定輸出中每行所允許的最大字符數(shù)。如果一個(gè)數(shù)據(jù)結(jié)構(gòu)無(wú)法在寬度限制之內(nèi)被格式化，將顯示盡可能多的內(nèi)容。

compact 影響長(zhǎng)序列（列表、元組、集合等等）的格式化方式。如果 compact 為假值（默認(rèn)）則序列的每一項(xiàng)將格式化為單獨(dú)的行。如果 compact 為真值，則每個(gè)輸出行格式化時(shí)將在 width 的限制之內(nèi)盡可能地容納多個(gè)條目。

如果 sort_dicts 為真值（默認(rèn)），字典在格式化時(shí)將基于鍵進(jìn)行排序，否則它們將按插入順序顯示。

如果 underscore_numbers 為真值，整數(shù)在格式化時(shí)將使用 _ 字符作為千位分隔符，否則不顯示下劃線（默認(rèn)）。

在 3.4 版更改: 增加了 compact 形參。

在 3.8 版更改: 增加了 sort_dicts 形參。

在 3.10 版更改: 添加了 underscore_numbers 形參。

在 3.11 版更改: 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', (...)))))))

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 above.

pprint.pp(object, *args, sort_dicts=False, **kwargs)?: 打印 object 的格式化表示并附帶一個(gè)換行符。如果 sort_dicts 為假值（默認(rèn)），字典將按鍵的插入順序顯示，否則將按字典鍵排序。 args 和 kwargs 將作為格式化形參被傳給 pprint()。

3.8 新版功能.

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 above.

>>>>>> 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)?

確定 object 的格式化表示是否“可讀”，或是否可被用來(lái)通過(guò) eval() 重新構(gòu)建對(duì)象的值。此函數(shù)對(duì)于遞歸對(duì)象總是返回 False。

>>>>>> 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 an RecursionError if it fails to detect a recursive object.

此外還定義了一個(gè)支持函數(shù)：

pprint.saferepr(object)?

Return a string representation of object, protected against recursion in some common data structures, namely instances of dict, list and tuple or 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 對(duì)象?

PrettyPrinter 的實(shí)例具有下列方法：

PrettyPrinter.pformat(object)?: 返回 object 格式化表示。這會(huì)將傳給 PrettyPrinter 構(gòu)造器的選項(xiàng)納入考慮。

PrettyPrinter.pprint(object)?: 在所配置的流上打印 object 的格式化表示，并附加一個(gè)換行符。

下列方法提供了與同名函數(shù)相對(duì)應(yīng)的實(shí)現(xiàn)。在實(shí)例上使用這些方法效率會(huì)更高一些，因?yàn)椴恍枰獎(jiǎng)?chuàng)建新的 PrettyPrinter 對(duì)象。

PrettyPrinter.isreadable(object)?: 確定對(duì)象的格式化表示是否“可讀”，或者是否可使用 eval() 重建對(duì)象值。請(qǐng)注意此方法對(duì)于遞歸對(duì)象將返回 False。如果設(shè)置了 PrettyPrinter 的 depth 形參并且對(duì)象深度超出允許范圍，此方法將返回 False。

PrettyPrinter.isrecursive(object)?: 確定對(duì)象是否需要遞歸表示。

此方法作為一個(gè)鉤子提供，允許子類修改將對(duì)象轉(zhuǎn)換為字符串的方式。默認(rèn)實(shí)現(xiàn)使用 saferepr() 實(shí)現(xiàn)的內(nèi)部方式。

PrettyPrinter.format(object, context, maxlevels, level)?: 返回三個(gè)值：字符串形式的 object 已格式化版本，指明結(jié)果是否可讀的旗標(biāo)，以及指明是否檢測(cè)到遞歸的旗標(biāo)。第一個(gè)參數(shù)是要表示的對(duì)象。第二個(gè)是以對(duì)象 id() 為鍵的字典，這些對(duì)象是當(dāng)前表示上下文的一部分（影響 object 表示的直接和間接容器）；如果需要呈現(xiàn)一個(gè)已經(jīng)在 context 中表示的對(duì)象，則第三個(gè)返回值應(yīng)當(dāng)為 True。對(duì) format() 方法的遞歸調(diào)用應(yīng)當(dāng)將容器的附加條目添加到此字典中。第三個(gè)參數(shù) maxlevels 給出了對(duì)遞歸的請(qǐng)求限制；如果沒(méi)有請(qǐng)求限制則其值將為 0。此參數(shù)應(yīng)當(dāng)不加修改地傳給遞歸調(diào)用。第四個(gè)參數(shù) level 給出于當(dāng)前層級(jí)；傳給遞歸調(diào)用的參數(shù)值應(yīng)當(dāng)小于當(dāng)前調(diào)用的值。

示例?

為了演示 pprint() 函數(shù)及其形參的幾種用法，讓我們從 PyPI 獲取關(guān)于某個(gè)項(xiàng)目的信息:

>>>>>> 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']

pprint() 以其基本形式顯示了整個(gè)對(duì)象:

>>>>>> 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'}

結(jié)果可以被限制到特定的 depth (更深層的內(nèi)容將使用省略號(hào)):

>>>>>> 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'}

此外，還可以設(shè)置建議的最大字符 width。如果一個(gè)對(duì)象無(wú)法被拆分，則將超出指定寬度:

>>>>>> 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'}

`pprint` --- 數(shù)據(jù)美化輸出?

PrettyPrinter 對(duì)象?

示例?

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