Python中字符串方法和str方法有什么区别？

Question

String是一个模块,str是一个类型.我发现str有方法,而str的一些方法与string相同.

>>>dir(str)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__',
'__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', 
'__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__',
'__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__',
'__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__',
'__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 
'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs',
'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace',
'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace',
'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 
'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper',
'zfill']

>>> dir(string)
['Formatter', 'Template', '_TemplateMetaclass', '__builtins__', '__doc__',
'__file__', '__name__', '__package__', '_float', '_idmap', '_idmapL', '_int', 
'_long', '_multimap', '_re', 'ascii_letters', 'ascii_lowercase', 'ascii_uppercase', 
'atof', 'atof_error', 'atoi', 'atoi_error', 'atol', 'atol_error', 'capitalize',   
'capwords', 'center', 'count', 'digits', 'expandtabs', 'find', 'hexdigits', 'index', 
'index_error', 'join', 'joinfields', 'letters', 'ljust', 'lower', 'lowercase',
'lstrip', 'maketrans', 'octdigits', 'printable', 'punctuation', 'replace', 'rfind',
'rindex', 'rjust', 'rsplit', 'rstrip', 'split', 'splitfields', 'strip', 'swapcase', 
'translate', 'upper', 'uppercase', 'whitespace', 'zfill']

这两套方法有什么区别？str或string可以使用彼此的方法吗？

Answer 1

string现在是一个已弃用的模块.你应该str总是使用对象.

>>> 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.
.
.
>>>help(string)
Help on module string:

NAME
    string - A collection of string operations (most are no longer used).

FILE
    /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/string.py

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

DESCRIPTION
    Warning: most of the code you see here isn't normally used nowadays.
    Beginning with Python 1.6, many of these functions are implemented as
    methods on the standard string object. They used to be implemented by
    a built-in module called strop, but strop is now obsolete itself.

Answer 2

当str方法被添加到Python时,许多现有的字符串模块被重写为str方法的瘦包装函数.例如,以下是字符串模块中较低函数的源代码:

# convert UPPER CASE letters to lower case
def lower(s):
    """lower(s) -> string

    Return a copy of the string s converted to lowercase.

    """
    return s.lower()