python 3 remove leading substring from string

Question

Suppose I have a filename ./file and I want to remove the leading ./ (if it starts with ./). What would be the best python way to do this? My take at this is:

if filename.startswith("./"):
  # remove leading ./
  filename = filename[2:]

Isn't there a more elegant way?

PS: it should remove the leading part only if it matches exactly, think of the following filenames:

./filename
.configfile
../file
./.configfile

`new_list = [element.replace("./", "") for element in old_list]` — Olvin Roght, Sep 10 '19 at 13:32
See [How to remove the left part of a string?](https://stackoverflow.com/questions/599953/how-to-remove-the-left-part-of-a-string) — khelwood, Sep 10 '19 at 13:33
@Itay, you can add `if element.startswith(".\")` if it's needed. It's just quick comment, not an nswer, feel the deffierence — Olvin Roght, Sep 10 '19 at 13:41

score 1 · Accepted Answer · answered Sep 10 '19 at 13:38

1

filenames = ['.configfile', './file1', './dir/file2']
filenames = [fn[2:] if fn.startswith("./") else fn for fn in filenames]

borrowing from your idea but doing it in one line

answered Sep 10 '19 at 13:38

user1443098

6,487
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score 1 · Answer 2 · answered Sep 10 '19 at 13:43

My personal preference would be the solution by @user1443098 But for completnes - using re

import re

pattern = re.compile(r'^\./')
files = ['./filename', '.configfile', '../file']
new_files = [re.sub(pattern, '', fname) for fname in files]
print(new_files)

score 0 · Answer 3 · answered Sep 10 '19 at 13:35

0

The way you do it is the ways it's usually done. Of course, you can always move it into a function:

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

answered Sep 10 '19 at 13:35

äymm

411
4
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score 0 · Answer 4 · answered Sep 10 '19 at 13:36

I would consider writing a helper function:

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

print(strip_prefix('./filename', './'))
print(strip_prefix('.configfile', './'))
print(strip_prefix('../file', './'))

score -1 · Answer 5 · answered Sep 10 '19 at 13:36

-1

Assuming you are using python3, the best way to deal with paths is trough the pathlib module:

if you only want the filename

from pathlib import Path
paths = ["./filename", ".configfile", "../file"]
only_filenames = [Path(f).name for f in paths]

answered Sep 10 '19 at 13:36

Hrabal

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This is not what the question asks, only exact matches to `./` should be removed, something like `../` should stay the same. Nowhere is stated that only the filename is wanted – FlyingTeller Sep 10 '19 at 13:42

score -3 · Answer 6 · answered Sep 10 '19 at 13:37

-3

if filename.startswith("./"):
    filename.lstrip("./")

answered Sep 10 '19 at 13:37

Domnic Amalan

94
4

3

that would mess up `./.configfile` – Chris Maes Sep 10 '19 at 13:42
Additionally, this would be a better answer if you explained how the code you provided answers the question. – pppery Sep 10 '19 at 19:04

python 3 remove leading substring from string

6 Answers6