python字符串函数

1，首字母大写

>>> s = 'ghostwu'
>>> s.capitalize()
'Ghostwu'

2，replace，替换

>>> s = 'my name is ghostwu, age is 20'
>>> s
'my name is ghostwu, age is 20'
>>> s.replace( '20', '30' )
'my name is ghostwu, age is 30'
>>> s
'my name is ghostwu, age is 20'
>>> 

查帮助

>>> help( str.replace )

如果是面向过程的函数用法，直接help( 函数名 )，如help( abs )

用法说明：

replace(...)
S.replace(old, new[, count]) -> string

Return a copy of string S with all occurrences of substring
old replaced by new. If the optional argument count is
given, only the first count occurrences are replaced.

接受3个参数，第一个需要替换的字符，第二个用什么字符去替换，第三个替换的次数，如果不传，默认全部替换

>>> str = '121212'
>>> str.replace( '1', 'g' )
'g2g2g2'
>>> str.replace( '1', 'g', 1 )
'g21212'
>>> str.replace( '1', 'g', 2 )
'g2g212'
>>> str.replace( '1', 'g', 3 )
'g2g2g2'

3，split：切割

>>> ip='127.0.0.1'
>>> ip
'127.0.0.1'
>>> ip.split( '.' )
['127', '0', '0', '1']
>>> ip.split( '.', 1 )
['127', '0.0.1']
>>> ip.split( '.', 2 )
['127', '0', '0.1']
>>> ip.split( '.', 3 )
['127', '0', '0', '1']
>>> 

4，用string模块，用法如下：

>>> import string
>>> help( string.capitalize )

>>> s = 'ghostwu'
>>> string.capitalize( s )
'Ghostwu'

>>> import string
>>> s = 'my name is ghostwu, age is 20'
>>> string.replace( s, '20', '30' )
'my name is ghostwu, age is 30'
>>> ip
'127.0.0.1'
>>> string.split( ip, '.' )
['127', '0', '0', '1']
>>> string.split( ip, '.', 1 )
['127', '0.0.1']
>>> 

5，filter：过滤， 利用这个函数，筛选出一个序列的偶数

>>> def isEven( n ):
...     if n % 2 == 0:
...             return True
... 
>>> isEven( 10 )
True
>>> isEven( 3 )
>>> range( 10 )
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> l = range( 10 )
>>> filter( isEven, l )
[0, 2, 4, 6, 8]
>>>