[d]一个用到maketrans跟tranlate的函数

[d]一个用到maketrans和tranlate的函数
#简化translate方法使用，包装起来。
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:
  allchars = string.maketrans('', '')
  delete = allchars.translate(allchars, keep.translate(allchars,delete))
  def translate(s):
  return s.translate(trans, delete)
  return translate

s1 = 'helloworld:8008208820'
num_only = translator(keep = string.digits)
print num_only(s1)
no_num = translator(delete = string.digits)
print no_num(s1)
special_tran = translator(frm = string.digits , to = '#')
print special_tran(s1)

以上translator函数，有些地方不懂，求大牛解析。
特别什么allchars = maketrans('','')




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