python之pprint模块简用

pprint module提供了可以按照某个格式正确的显示python已知类型数据的一种方法，这种格式可被解析器解析, 又很易读。但是，如果已知格式的数据对象不是python的基础类型，这种表示方法就有可能加载失败。这种情况一般是对象为 files, sockets, classes, or instances are included, as well as many other built-in objects which are not representable as Python constants。

该方法输出将对象的输出分隔成单行显示，并在宽度设置不适合时，将其分成多行显示。

class pprint.PrettyPrinter(indent=1,width=80,depth=None,stream=None)

pprint.pformat(object,indent=1,width=80,depth=None)仅仅想获得数据而不是输出数据也可以用pformat

Return the formatted representation of object as a string. indent,widthanddepth will be passed to thePrettyPrinter constructor as formatting parameters.

pprint.pprint(object,stream=None,indent=1,width=80,depth=None)

Prints the formatted representation of object on stream, followed by anewline.

pprint.isreadable(object)

Determine if the formatted representation of object is “readable,” or can be used to reconstruct the value usingeval(). This always returnsFalse for recursive objects.

>>> import sys>>> import pprint>>> pprint.pprint(sys.path)['D:/Python/tmp', 'D:\\Python\\tmp', 'C:\\Python27\\Lib\\idlelib', 'C:\\Python27\\lib\\site-packages\\zope.interface-4.0.0-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\pyopenssl-0.13-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\scrapy-0.14.4-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\w3lib-1.2-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\mysql_python-1.2.3-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\paramiko-1.9.0-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\pycrypto-2.6-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\requests-2.0.0-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\reportlab-2.7-py2.7-win32.egg', 'C:\\Windows\\system32\\python27.zip', 'C:\\Python27\\DLLs', 'C:\\Python27\\lib', 'C:\\Python27\\lib\\plat-win', 'C:\\Python27\\lib\\lib-tk', 'C:\\Python27', 'C:\\Python27\\lib\\site-packages', 'C:\\Python27\\lib\\site-packages\\wx-2.8-msw-unicode']>>> print sys.path #一行显示，显示很长['D:/Python/tmp', 'D:\\Python\\tmp', 'C:\\Python27\\Lib\\idlelib', 'C:\\Python27\\lib\\site-packages\\zope.interface-4.0.0-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\pyopenssl-0.13-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\scrapy-0.14.4-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\w3lib-1.2-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\mysql_python-1.2.3-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\paramiko-1.9.0-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\pycrypto-2.6-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\requests-2.0.0-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\reportlab-2.7-py2.7-win32.egg', 'C:\\Windows\\system32\\python27.zip', 'C:\\Python27\\DLLs', 'C:\\Python27\\lib', 'C:\\Python27\\lib\\plat-win', 'C:\\Python27\\lib\\lib-tk', 'C:\\Python27', 'C:\\Python27\\lib\\site-packages', 'C:\\Python27\\lib\\site-packages\\wx-2.8-msw-unicode']>>> string = pprint.pformat(sys.path)>>> string #还是一行"['D:/Python/tmp',\n 'D:\\\\Python\\\\tmp',\n 'C:\\\\Python27\\\\Lib\\\\idlelib',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\zope.interface-4.0.0-py2.7-win32.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\pyopenssl-0.13-py2.7-win32.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\scrapy-0.14.4-py2.7.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\w3lib-1.2-py2.7.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\mysql_python-1.2.3-py2.7-win32.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\paramiko-1.9.0-py2.7.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\pycrypto-2.6-py2.7-win32.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\requests-2.0.0-py2.7.egg',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\reportlab-2.7-py2.7-win32.egg',\n 'C:\\\\Windows\\\\system32\\\\python27.zip',\n 'C:\\\\Python27\\\\DLLs',\n 'C:\\\\Python27\\\\lib',\n 'C:\\\\Python27\\\\lib\\\\plat-win',\n 'C:\\\\Python27\\\\lib\\\\lib-tk',\n 'C:\\\\Python27',\n 'C:\\\\Python27\\\\lib\\\\site-packages',\n 'C:\\\\Python27\\\\lib\\\\site-packages\\\\wx-2.8-msw-unicode']">>> print string #输出格式变成了单行['D:/Python/tmp', 'D:\\Python\\tmp', 'C:\\Python27\\Lib\\idlelib', 'C:\\Python27\\lib\\site-packages\\zope.interface-4.0.0-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\pyopenssl-0.13-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\scrapy-0.14.4-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\w3lib-1.2-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\mysql_python-1.2.3-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\paramiko-1.9.0-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\pycrypto-2.6-py2.7-win32.egg', 'C:\\Python27\\lib\\site-packages\\requests-2.0.0-py2.7.egg', 'C:\\Python27\\lib\\site-packages\\reportlab-2.7-py2.7-win32.egg', 'C:\\Windows\\system32\\python27.zip', 'C:\\Python27\\DLLs', 'C:\\Python27\\lib', 'C:\\Python27\\lib\\plat-win', 'C:\\Python27\\lib\\lib-tk', 'C:\\Python27', 'C:\\Python27\\lib\\site-packages', 'C:\\Python27\\lib\\site-packages\\wx-2.8-msw-unicode']>>> 

>>> stuff = ['spam','eggs','lumberjack','knight','ni']>>> pprint.pprint(stuff)['spam', 'eggs', 'lumberjack', 'knight', 'ni']>>> print stuff['spam', 'eggs', 'lumberjack', 'knight', 'ni']>>> stuff.insert(0,stuff)>>> pprint.pprint(stuff)#If stream is None, sys.stdout is used.  This may be used in the interactive interpreter instead of a print statement# for inspecting values.[<Recursion on list with id=33573024>, 'spam', 'eggs', 'lumberjack', 'knight', 'ni']>>> print stuff[[...], 'spam', 'eggs', 'lumberjack', 'knight', 'ni']>>> 

>>> pprint.isreadable(stuff)#Determine if the formatted representation of object is “readable“False>>> pprint.isreadable(sys.path)True>>>

# This example demonstrates several uses of the pprint() function and its parameters.

如下例，依次为：

#list中包含tuple
#按照指定深度来显示stuff内容
#The number of levels which may be printed is controlled by depth; if the data structure being printed is too deep, the next contained level is replaced by ....
#The desired output width is constrained using the width parameter; the default is 80 characters.

If a structure cannot be formatted within the constrained width, a best effort will be made.

>>> tup = ('spam',('eggs',('lumberjack',)))>>> stuff = ['a'*5, tup, ['b'*5, 'c'*5],['c'*5, 'd'*5]]>>> stuff['aaaaa', ('spam', ('eggs', ('lumberjack',))), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff)['aaaaa', ('spam', ('eggs', ('lumberjack',))), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff,depth=3)['aaaaa', ('spam', ('eggs', (...,))), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff,depth=4)['aaaaa', ('spam', ('eggs', ('lumberjack',))), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff,depth=2)['aaaaa', ('spam', (...)), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff,width=40)['aaaaa', ('spam', ('eggs', ('lumberjack',))), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff,width=80)['aaaaa', ('spam', ('eggs', ('lumberjack',))), ['bbbbb', 'ccccc'], ['ccccc', 'ddddd']]>>> pprint.pprint(stuff,width=3)['aaaaa', ('spam',  ('eggs',   ('lumberjack',))), ['bbbbb',  'ccccc'], ['ccccc',  'ddddd']]>>> 

总的来说，感觉目前用处不是很大，没有什么特别的地方，就是对输出的一种格式化。