Remove a Prefix from a String [Duplicate]

Question

I am trying to do the following, in a clear pythonic way:

def remove_prefix(str, prefix):
    return str.lstrip(prefix)

print remove_prefix('template.extensions', 'template.')

This gives:

xtensions

Which is not what I was expecting (extensions). Obviously (stupid me), because I have used lstrip wrongly: lstrip will remove all characters which appear in the passed chars string, not considering that string as a real string, but as "a set of characters to remove from the beginning of the string".

Is there a standard way to remove a substring from the beginning of a string?

Accepted Answer

I don't know about "standard way".

def remove_prefix(text, prefix):
    if text.startswith(prefix):
        return text[len(prefix):]
    return text  # or whatever

As noted by @Boris and @Stefan, on Python 3.9+ you can use

text.removeprefix(prefix)

with the same behavior.

Answer 2

Short and sweet:

def remove_prefix(text, prefix):
    return text[text.startswith(prefix) and len(prefix):]

Answer 3

What about this (a bit late):

def remove_prefix(s, prefix):
    return s[len(prefix):] if s.startswith(prefix) else s

Answer 4

I think you can use methods of the str type to do this. There's no need for regular expressions:

def remove_prefix(text, prefix):
    if text.startswith(prefix): # only modify the text if it starts with the prefix
         text = text.replace(prefix, "", 1) # remove one instance of prefix
    return text

Answer 5

regex solution (The best way is the solution by @Elazar this is just for fun)

import re
def remove_prefix(text, prefix):
    return re.sub(r'^{0}'.format(re.escape(prefix)), '', text)

>>> print remove_prefix('template.extensions', 'template.')
extensions

Answer 6

def remove_prefix(str, prefix):
    if str.startswith(prefix):
        return str[len(prefix):]
    else:
        return str

As an aside note, str is a bad name for a variable because it shadows the str type.

Remove a Prefix from a String [Duplicate]

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Sarah Jenkins