如何从列表中的某些字符串中删除特定字符串？

Question

I've been trying to figure out a more universal fix for my code and having a hard time with it. This is what I have:

lst = ['Thursday, June ##', 'some string', 'another string', 'etc', 'Friday, June ##', 'more strings', 'etc']

I'm trying to remove everything after the comma in the strings that contain commas (which can only be the day of the week strings).

My current fix that works is:

new_lst = [x[:-9] if ',' in x else x for x in lst]

But this won't work for every month since they're not always going to be a 4 letter string ('June'). I've tried splitting at the commas and then removing any string that starts with a space but it wasn't working properly so I'm not sure what I'm doing wrong.

Answer 1

We can use a list comprehension along with split() here:

lst = ['Thursday, June ##', 'some string', 'another string', 'etc', 'Friday, June ##', 'more strings', 'etc']
output = [x.split(',', 1)[0] for x in lst]
print(output)
# ['Thursday', 'some string', 'another string', 'etc', 'Friday', 'more strings', 'etc']

Answer 2

With regex :

>>> import re
>>> lst = [re.sub(r',.*', '', x) for x in lst]
>>> lst
['Thursday,', 'some string', 'another string', 'etc', 'Friday,', 'more strings', 'etc']

However, this is slower than the split answer

Answer 3

You can use re.search in the following way:

import re
lst = ['Thursday, June ##', 'some string', 'another string', 'etc', 'Friday, June ##', 'more strings', 'etc']
for i, msg in enumerate(lst):
    match = re.search(",", msg)
    if match != None:
        lst[i] = msg[:match.span()[0]]
print(lst)

Output:

['Thursday', 'some string', 'another string', 'etc', 'Friday', 'more strings', 'etc']