先來看下關於這兩個函式的官方定義：

        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.

        string.translate(s, table[, deletechars])：Delete all characters from s that are in deletechars (if present), and then translate the characters using table, which must be a 256-character string giving the translation for each character value, indexed by its ordinal. If table is None, then only the character deletion step is performed.

        下面的程式碼是對這兩個函式進行的封裝：

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import string

def translator(frm='', to='', delete='', keep=None):
    if len(to) == 1:
        to = to * len(frm)
    
    trans = string.maketrans(frm, to)
    if keep is not None:
        trans_all = string.maketrans('', '')
        #keep.translate(trans_all, delete)，從要保留的字元中剔除要刪除的字元
        #trans_all.translate(trans_all, keep.translate(trans_all, delete))，從翻譯表中刪除要保留的字元，即取保留字元的補集
        delete = trans_all.translate(trans_all, keep.translate(trans_all, delete))
        
    def translate(s):
        return s.translate(trans, delete)
        
    return translate

if __name__ == '__main__':
    #result:12345678
    digits_only = translator(keep=string.digits)
    print digits_only('Eric chen: 1234-5678')
    
    #result:Eric chen: -
    no_digits = translator(delete=string.digits)
    print no_digits('Eric chen: 1234-5678')
    
    #result:Eric chen: ****-****
    digits_to_hash = translator(frm=string.digits, to='*')
    print digits_to_hash('Eric chen: 1234-5678')
 

        其實呼叫maketrans函式時，已經完成了轉換。例如string.maketrans('ABCD', 'abcd'),呼叫完成後，翻譯表生成的包含256個字元的字串（忽略不可列印字元）為“!"#$%&'()*+,-./0123456789:;<=>?@abcdEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~”，該翻譯表中的原“ABCD”的位置已被“abcd”替換。

        當你把t作為第一個引數傳入translate方法時，原字串中的每一個字元c，在處理完成後都會被翻譯成字元t[ord(c)]。

        For Unicode objects, the translate() method does not accept the optional deletechars argument. Instead, it returns a copy of the s 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.

        下面的程式碼是對unicode字串進行過濾：

import sets
class Keeper(object):
    def __init__(self, keep):
        self.keep = sets.Set(map(ord, keep))
    
    def __getitem__(self, n):
        if n not in self.keep:
            return None
        return unichr(n)
    
    def __call__(self, s):
        return unicode(s).translate(self)

makeFilter = Keeper

if __name__ == '__main__':
    #result:人民
    just_people = makeFilter(u'人民')
    print just_people(u'中華人民共和國成立了')

    #刪除unicode字元
    #result:中華共和國成立了!
    translate_table = dict((ord(char), None) for char in u'人民')
    print unicode(u'中華人民共和國成立了!').translate(translate_table)
    
    #替換unicode字元
    #result:中華**共和國成立了!
    translate_table = dict((ord(char), u'*') for char in u'人民')
    print unicode(u'中華人民共和國成立了!').translate(translate_table)