python字符串函数

Posted 2020-10-27 ghostwu

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

1 >>> str = ‘121212‘
2 >>> str.replace( ‘1‘, ‘g‘ )
3 ‘g2g2g2‘
4 >>> str.replace( ‘1‘, ‘g‘, 1 )
5 ‘g21212‘
6 >>> str.replace( ‘1‘, ‘g‘, 2 )
7 ‘g2g212‘
8 >>> str.replace( ‘1‘, ‘g‘, 3 )
9 ‘g2g2g2‘

3，split：切割

 1 >>> ip=‘127.0.0.1‘
 2 >>> ip
 3 ‘127.0.0.1‘
 4 >>> ip.split( ‘.‘ )
 5 [‘127‘, ‘0‘, ‘0‘, ‘1‘]
 6 >>> ip.split( ‘.‘, 1 )
 7 [‘127‘, ‘0.0.1‘]
 8 >>> ip.split( ‘.‘, 2 )
 9 [‘127‘, ‘0‘, ‘0.1‘]
10 >>> ip.split( ‘.‘, 3 )
11 [‘127‘, ‘0‘, ‘0‘, ‘1‘]
12 >>> 

4，用string模块，用法如下：

1 >>> import string
2 >>> help( string.capitalize )
3 
4 >>> s = ‘ghostwu‘
5 >>> string.capitalize( s )
6 ‘Ghostwu‘

 1 >>> import string
 2 >>> s = ‘my name is ghostwu, age is 20‘
 3 >>> string.replace( s, ‘20‘, ‘30‘ )
 4 ‘my name is ghostwu, age is 30‘
 5 >>> ip
 6 ‘127.0.0.1‘
 7 >>> string.split( ip, ‘.‘ )
 8 [‘127‘, ‘0‘, ‘0‘, ‘1‘]
 9 >>> string.split( ip, ‘.‘, 1 )
10 [‘127‘, ‘0.0.1‘]
11 >>> 

5，filter：过滤， 利用这个函数，筛选出一个序列的偶数

 1 >>> def isEven( n ):
 2 ...     if n % 2 == 0:
 3 ...             return True
 4 ... 
 5 >>> isEven( 10 )
 6 True
 7 >>> isEven( 3 )
 8 >>> range( 10 )
 9 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
10 >>> l = range( 10 )
11 >>> filter( isEven, l )
12 [0, 2, 4, 6, 8]
13 >>>