How to remove all characters after a specific character in python?

Split on your separator at most once, and take the first piece:

sep = '...'
stripped = text.split(sep, 1)[0]

You didn't say what should happen if the separator isn't present. Both this and Alex's solution will return the entire string in that case.

Assuming your separator is '...', but it can be any string.

text = 'some string... this part will be removed.'
head, sep, tail = text.partition('...')

>>> print head
some string

If the separator is not found, head will contain all of the original string.

The partition function was added in Python 2.5.

S.partition(sep) -> (head, sep, tail)

Searches for the separator sep in S, and returns the part before it, the separator itself, and the part after it. If the separator is not found, returns S and two empty strings.

If you want to remove everything after the last occurrence of separator in a string I find this works well:

<separator>.join(string_to_split.split(<separator>)[:-1])

For example, if string_to_split is a path like root/location/child/too_far.exe and you only want the folder path, you can split by "/".join(string_to_split.split("/")[:-1]) and you'll get root/location/child

Without a regular expression (which I assume is what you want):

def remafterellipsis(text):
  where_ellipsis = text.find('...')
  if where_ellipsis == -1:
    return text
  return text[:where_ellipsis + 3]

or, with a regular expression:

import re

def remwithre(text, there=re.compile(re.escape('...')+'.*')):
  return there.sub('', text)