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：
pprint.
PrettyPrinter
(
indent=1
,
width=80
,
depth=None
,
stream=None
,
*
,
compact=False
)
¶
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
will be formatted on each output line.
3.4 版改变： 添加 compact 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
)
¶
返回格式化表示
object
以字符串形式。
indent
,
width
,
depth
and
compact
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。
pprint.
pprint
(
object
,
stream=None
,
indent=1
,
width=80
,
depth=None
,
*
,
compact=False
)
¶
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
and
compact
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。
>>> 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
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.
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': [{...}, {...}]}