python 查询数据类型及帮助的使用

合理使用python提供的内置函数提供的信息，可以很好的帮助我们编程，这里介绍3个函数：type(),dir(),help()

type(x)
type()可以接收任何东西作为参数――并返回它的数据类型。
整型、字符串、列表、字典、元组、函数、类、模块，甚至类型对象都可以作为参数被 type 函数接受。

In [66]: type(2)
Out[66]: int

In [67]: type('ssdgg')
Out[67]: str

In [68]: alist = []

In [69]: type(alist)
Out[69]: list

In [70]: import sys

In [71]: type(sys)
Out[71]: module

dir()函数使用方法
使用dir()函数可以查看对像内所有属于及方法，在python中任何东西都是对像，一种，一个等，都有自己的属性和方法，除了常用方法外，其它的你不需要全部记住它，交给dir()函数就好了。dir()函数操作方法很简单，只需要把你想要查询和对像添写到( )括号中就可以使用了，它返回包含要查询对象的所有属性名称的列表

In [107]: dir([])
Out[107]:
['__add__',
 '__class__',
 '__contains__',
 '__delattr__',
 '__delitem__',
 '__delslice__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattribute__',
 '__getitem__',
 '__getslice__',
 '__gt__',
 '__hash__',
 '__iadd__',
 '__imul__',
 '__init__',
 '__iter__',
 '__le__',
 '__len__',
 '__lt__',
 '__mul__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__reversed__',
 '__rmul__',
 '__setattr__',
 '__setitem__',
 '__setslice__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 'append',
 'count',
 'extend',
 'index',
 'insert',
 'pop',
 'remove',
 'reverse',
 'sort']

要查看python某个模块可以干什么，先要导入模块，之后用上面讲过的方式查看就可以。比如要查看都可以干什么，可以像下边这样操作：

In [108]: import sys

In [109]: dir(sys)
Out[109]:
['__displayhook__',
 '__doc__',
 '__excepthook__',
 '__name__',
 '__package__',
 '__stderr__',
 '__stdin__',
 '__stdout__',
 '_clear_type_cache',
 '_current_frames',
 '_getframe',
 'api_version',
 'argv',
 'builtin_module_names',
 'byteorder',
 'call_tracing',
 'callstats',
 'copyright',
 'displayhook',
 'dont_write_bytecode',
 'exc_clear',
 'exc_info',
 'exc_traceback',
 'exc_type',
 'exc_value',
 'excepthook',
 'exec_prefix',
 'executable',
 'exit',
 'exitfunc',
 'flags',
 'float_info',
 'getcheckinterval',
 'getdefaultencoding',
 'getdlopenflags',
 'getfilesystemencoding',
 'getprofile',
 'getrecursionlimit',
 'getrefcount',
 'getsizeof',
 'gettrace',
 'hexversion',
 'last_traceback',
 'last_type',
 'last_value',
 'maxint',
 'maxsize',
 'maxunicode',
 'meta_path',
 'modules',
 'path',
 'path_hooks',
 'path_importer_cache',
 'platform',
 'prefix',
 'ps1',
 'ps2',
 'ps3',
 'py3kwarning',
 'setcheckinterval',
 'setdlopenflags',
 'setprofile',
 'setrecursionlimit',
 'settrace',
 'stderr',
 'stdin',
 'stdout',
 'subversion',
 'version',
 'version_info',
 'warnoptions']

help()函数的作用
在使用python来编写代码时，会经常使用python自带函数或模块，一些不常用的函数或是模块的用途不是很清楚，这时候就需要用到help函数来查看帮助。
这里要注意下，help()函数是查看函数或模块用途的详细说明，而dir()函数是查看函数或模块内的操作方法都有什么，输出的是方法列表。
help()括号内填写参数，操作方法很简单。例如：

In [110]: help('dir')
Help on built-in function dir in module __builtin__:

dir(...)
    dir([object]) -> list of strings

    If called without an argument, return the names in the current scope.
    Else, return an alphabetized list of names comprising (some of) the attributes
    of the given object, and of attributes reachable from it.
    If the object supplies a method named __dir__, it will be used; otherwise
    the default dir() logic is used and returns:
      for a module object: the module's attributes.
      for a class object:  its attributes, and recursively the attributes
        of its bases.
      for any other object: its attributes, its class's attributes, and
        recursively the attributes of its class

使用help函数查看帮助实例：
在写help()函数使用方法时说过，括号中填写参数，那在这里要注意参数的形式：
1.查看一个模块的帮助

In [1]: help('sys')
Help on built-in module sys:

NAME
    sys

FILE
    (built-in)

MODULE DOCS
    http://docs.python.org/library/sys

DESCRIPTION
    This module provides access to some objects used or maintained by the
    interpreter and to functions that interact strongly with the interpreter.

    Dynamic objects:

2.查看一个数据类型的帮助

In [1]: help('str')
Help on class str in module __builtin__:

class str(basestring)
 | str(object) -> string
 |
 | Return a nice string representation of the object.
 | If the argument is a string, the return value is the same object.
 |
 | Method resolution order:
 | str
 | basestring
 | object
 |
 | Methods defined here:
 |
 | __add__(...)
 | x.__add__(y) <==> x+y
 |
 | __contains__(...)
 | x.__contains__(y) <==> y in x
 |
 | __eq__(...)
 | x.__eq__(y) <==> x==y

[2]+ Stopped                 ipython
[root@ftp ~]# ipython
Python 2.6.6 (r266:84292, Jul 23 2015, 15:22:56)
Type "copyright", "credits" or "license" for more information.

IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.

返回字符串的方法及详细说明

a = [1,2,3]
help(a)
Help on list object:
class list(object)
 | list() -> new empty list
 | list(iterable) -> new list initialized from iterable's items
 |
 |  Methods defined here:
 |
 |  __add__(...)
 |      x.__add__(y) <==> x+y
 |
 |  __contains__(...)
 |      x.__contains__(y) <==> y in x
 |
 |  __delitem__(...)
 |      x.__delitem__(y) <==> del x[y]
 |
 |  __delslice__(...)
 |      x.__delslice__(i, j) <==> del x[i:j]
 |
 |      Use of negative indices is not supported.
 |
 |  __eq__(...)
 |      x.__eq__(y) <==> x==y
 |
 |  __ge__(...)
 |      x.__ge__(y) <==> x>=y
 |
 |  __getattribute__(...)
 |      x.__getattribute__('name

这时help(a)则会打开list的操作方法

help(a.append)
Help on built-in function append:
append(...)
    L.append(object) -- append object to end