python的一个优势是有着大量自带和在线的模块(module)资源，可以提供丰富的功能，在使用这些模块的时候，如果每次都去网站找在线文档会过于耗费时间，结果也不一定准确。因此这里介绍下python自带的查看帮助功能，可以在编程时不中断地迅速找到所需模块和函数的使用方法。
通用帮助函数help()
在python命令行中键入help(),可以看到：
>>> help() Welcome to Python 3.5's help utility! If this is your first time using Python, you should definitely check out the tutorial on the Internet at http://docs.python.org/3.5/tutorial/. Enter the name of any module, keyword, or topic to get help on writing Python programs and using Python modules. To quit this help utility and return to the interpreter, just type "quit". To get a list of available modules, keywords, symbols, or topics, type "modules", "keywords", "symbols", or "topics". Each module also comes with a one-line summary of what it does; to list the modules whose name or summary contain a given string such as "spam", type "modules spam". help>
进入help帮助文档界面，根据屏幕提示可以继续键入相应关键词进行查询，继续键入modules可以列出当前所有安装的模块：
help> modules Please wait a moment while I gather a list of all available modules... AutoComplete _pyio filecmp pyscreeze AutoCompleteWindow _random fileinput pytweening ...... Enter any module name to get more help. Or, type "modules spam" to search for modules whose name or summary contain the string "spam".
模块帮助查询
查看.py结尾的普通模块help(module_name)
例如要查询math模块的使用方法，可以如下操作：
>>> import math >>> help(math) Help on built-in module math: NAME math DESCRIPTION This module is always available. It provides access to the mathematical functions defined by the C standard. FUNCTIONS acos(...) acos(x) Return the arc cosine (measured in radians) of x. ... >>>
查看内建模块sys.bultin_modulenames
>>> import sys>>> sys.builtin_module_names
('_ast', '_bisect', '_codecs', '_codecs_cn', '_codecs_hk', ... 'zlib')
>>>
查询函数信息
查看模块下所有函数dir(module_name)
如我们需要列举出math模块下所有的函数名称
>>> dir(math) ['__doc__', '__loader__', '__name__',...] >>>
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