Strip() Function Using Regex

Question

I'm trying to recreate the strip() function of python using Regex. It's the last practice problem from Automate the Boring Stuff with Python. Here's my code:

import re

stripChar = input('Enter character to strip: ')
context = input('Enter string to strip: ')
stripContext = None


def strip(char, string):
    if stripChar == "":
        regsp = re.compile(r'^\s+|\s+$')
        stripContext = regsp.sub("", context)
        return stripContext
    else:
        stripContext = re.sub(r'^(char)+', "", string)
        return stripContext

print(strip(stripChar, context))

In line 16, if I replace (char) with any random character, the program is working. However, I can't seem to make a custom variable work there. What am I doing wrong there?

Edit: Stack is saying it's a duplicate of this question. It's not because it' s purely around Regex not only Python.

Answer 1

I slightly changed your script like this,

def strip(char, string):
    if char == "":                # not "stripChar"
        regsp = re.compile(r'^\s+|\s+$')
        stripContext = regsp.sub("", string)
        return stripContext
    else:                       # some changes are here in this else statement
        stripContext = re.sub(r'^{}+|{}+$'.format(char,char), "", strip("",string))
        return stripContext

print(strip(stripChar, context))

Output:

Enter character to strip: e
Enter string to strip:   efdsafdsaeeeeeeeeee
fdsafdsa

Answer 2

You could do it like this using re.sub

import re

def strip(string, chars=' \n\r\t'):
    return re.sub(r'(?:^[{chars}]+)|(?:[{chars}]+$)'.format(chars=re.escape(chars)), '', string)

It uses re.escape, so users can enter characters like \ and [ that have meaning withing regex strings. It also uses the ^ and $ regex tokens so that only groups of matching characters at the front and end of the string are matched.