我想在第一次出现时用一个字符分割一个字符串，该字符属于一个字符列表。 如何在python中做到这一点？

Question

Basically, I have a list of special characters. I need to split a string by a character if it belongs to this list and exists in the string. Something on the lines of:

def find_char(string):

  if string.find("some_char"):
     #do xyz with some_char
  elif string.find("another_char"):
     #do xyz with another_char
  else:
     return False

and so on. The way I think of doing it is:

def find_char_split(string):
     char_list = [",","*",";","/"]
     for my_char in char_list:
         if string.find(my_char) != -1:
             my_strings = string.split(my_char)
             break
         else:
             my_strings = False

     return my_strings

Is there a more pythonic way of doing this? Or the above procedure would be fine? Please help, I'm not very proficient in python.

(EDIT): I want it to split on the first occurrence of the character, which is encountered first. That is to say, if the string contains multiple commas, and multiple stars, then I want it to split by the first occurrence of the comma . Please note, if the star comes first, then it will be broken by the star.

Answer 1

I would favor using the re module for this because the expression for splitting on multiple arbitrary characters is very simple:

r'[,*;/]'

The brackets create a character class that matches anything inside of them. The code is like this:

import re

results = re.split(r'[,*;/]', my_string, maxsplit=1)

The maxsplit argument makes it so that the split only occurs once.

If you are doing the same split many times, you can compile the regex and search on that same expression a little bit faster (but see Jon Clements' comment below ):

c = re.compile(r'[,*;/]')
results = c.split(my_string)

If this speed up is important (it probably isn't) you can use the compiled version in a function instead of having it re compile every time. Then make a separate function that stores the actual compiled expression:

def split_chars(chars, maxsplit=0, flags=0, string=None):
    # see note about the + symbol below
    c = re.compile('[{}]+'.format(''.join(chars)), flags=flags)
    def f(string, maxsplit=maxsplit):
        return c.split(string, maxsplit=maxsplit)
    return f if string is None else f(string)

Then:

special_split = split_chars(',*;/', maxsplit=1)
result = special_split(my_string)

But also:

result = split_chars(',*;/', my_string, maxsplit=1)

The purpose of the + character is to treat multiple delimiters as one if that is desired (thank you Jon Clements). If this is not desired, you can just use re.compile('[{}]'.format(''.join(chars))) above. Note that with maxsplit=1 , this will not have any effect.

Finally: have a look at this talk for a quick introduction to regular expressions in Python, and this one for a much more information packed journey.