Test whether a file name has the correct naming convention in Python

Question

How can I test whether a file name has the correct naming convention in Python? Say I want file names to end with the string _v and then some number and then .txt. How would I do that? I have some example code which expresses my idea, but doesn't actually work:

fileName = 'name_v011.txt'
def naming_convention(fileName):
    convention="_v%d.txt"
    if fileName.endswith(convention) == True:
        print "good"
    return
naming_convention(fileName)

Answer 1

You could use a regular expression using Python's re module:

import re

if re.match(r'^.*_v\d+\.txt$', filename):
    pass  # valid
else:
    pass  # invalid

Let's pick the regular expression apart:

• ^ matches the start of the string
• .* matches anything
• _v matches _v literally
• \d+ matches one or more digits
• \.txt matches .txt literally
• $ matches the end of the string