python之string.maketrans和str.translate

转载地址：http://blog.csdn.net/skyin333/article/details/8661131

示例：

[python] view plain copy

1. import string    
2.     
3. s = 'abcd--dcba'    
4.     
5. # 参数from和to的长度必须一致    
6. table = string.maketrans('', '')   # type(table) is 'str'  
7. print(s.translate(table))   # 输出 abcd--dcba  
8.   
9. table = string.maketrans('ab', '12')  
10. print(s.translate(table))   # 输出 12cd--dc21  
11.   
12. # 将先删除'ad'，然后再转换  
13. print(s.translate(table, 'ad'))     # 输出 2c--c2  

doc:

string.maketrans(from,to)

Return a translation table suitable for passing to translate(), that will map each character in from into the character at the same position in to;from and to must have the same length.

Note

Don’t use strings derived from lowercase and uppercase as arguments; in some locales, these don’t have the same length. For case conversions, always usestr.lower() andstr.upper().

str.translate(table[,deletechars])

Return a copy of the string where all characters occurring in the optional argument deletechars are removed, and the remaining characters have been mapped through the given translation table, which must be a string of length 256.

You can use the maketrans() helper function in the string module to create a translation table. For string objects, set the table argument to None for translations that only delete characters:

>>> 'read this short text'.translate(None, 'aeiou')'rd ths shrt txt'

New in version 2.6: Support for a None table argument.

For Unicode objects, the translate() method does not accept the optionaldeletechars argument. Instead, it returns a copy of thes where all characters have been mapped through the given translation table which must be a mapping of Unicode ordinals to Unicode ordinals, Unicode strings or None. Unmapped characters are left untouched. Characters mapped to None are deleted. Note, a more flexible approach is to create a custom character mapping codec using the codecs module (see encodings.cp1251 for an example).