python之string.maketrans和str.translate

示例：

import string  
  
s = 'abcd--dcba'  
  
# 参数from和to的长度必须一致  
table = string.maketrans('', '')   # type(table) is 'str'
print(s.translate(table))   # 输出 abcd--dcba

table = string.maketrans('ab', '12')
print(s.translate(table))   # 输出 12cd--dc21

# 将先删除'ad'，然后再转换
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).