Get file extension from filename with Python

Several times I had to put some code together some Python code to get the extension from a filename.

It was required for it to work OK with complex extensions, like ".tar.gz", and remain functional when you have dots in the filename, like in this case: "some.filename.1.v2.tar.gz".

After trying several options, the one that did the trick was using regular expressions, wrapped in a little function.

Here the case for keeping the ".", and getting the extension in the fashion ".tar.gz" or ".png":

	import re
	def get_extension(filename):
	regex = re.compile(r'^.*?.(?P<ext>.tar\.gz|.tar\.bz2|.\w+)$')
	return regex.match(filename).group('ext')

view raw gistfile1.py hosted with ❤ by GitHub

Here the case for not keeping the ".", and getting the extension in the fashion "tar.gz" or "png":

	import re
	def get_extension(filename):
	regex = re.compile(r'^.*?[.](?P<ext>tar\.gz|tar\.bz2|\w+)$')
	return regex.match(filename).group('ext')

view raw get_extension.py hosted with ❤ by GitHub

Et voilà! :D