Check for valid file extension

Question

On user input I am trying to validate they typed an appropriate file extension. For example:

file1 = input('Enter the file name ending in ".txt": ')

I'd like to validate that they entered '.txt'. Right now I'm doing very basic checking. However, the check below doesn't really validate that the file 'ends' in .txt.

if '.txt' not in file_name:
    print('Include file extension (example): ".txt"')

So I suppose its validating only 'txt' characters exist after '.' but only if that is the final '.', for example, I wouldn't want it to accidentally catch on "dinosoars" in baby.dinosoars.txt.

Possible duplicate of [Checking file extension](http://stackoverflow.com/questions/5899497/checking-file-extension) — Padraic Cunningham, May 14 '16 at 23:55

score 4 · Accepted Answer · answered May 14 '16 at 23:46

4

If you make your filename into a string s, you can use endswith:

if s.endswith('.txt'):
...
elif s.endswith('.test'):
...

Or the case-insensitive version (and eliminate any else-if chain)

s.lower().endswith(('.png', '.jpg', '.jpeg'))

answered May 14 '16 at 23:46

sjwarner

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score 1 · Answer 2 · answered May 14 '16 at 23:46

1

Why not use endswith instead?

if not file_name.endswith(extension):
    #exec code

answered May 14 '16 at 23:46

Pythonista

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schafle · Answer 3 · 2016-05-14T23:47:31.343

1

This should work:

if file_name.endswith(".txt"):
    print "something"

edited May 14 '16 at 23:47

answered May 14 '16 at 23:46

schafle

615
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`endswith` instead of `ends_with` and `print` needs parenthesis in Python 3.x – Pythonista May 14 '16 at 23:47

Check for valid file extension

3 Answers3