CODEWITHSUNDEEP
pythonregex
Pushpak Dagade
Pushpak Dagade

Reputation: 6440

Getting file extension using pattern matching in python

I am trying to find the extension of a file, given its name as a string. I know I can use the function os.path.splitext but it does not work as expected in case my file extension is .tar.gz or .tar.bz2 as it gives the extensions as gz and bz2 instead of tar.gz and tar.bz2 respectively.
So I decided to find the extension of files myself using pattern matching.

print re.compile(r'^.*[.](?P<ext>tar\.gz|tar\.bz2|\w+)$').match('a.tar.gz')group('ext')
>>> gz            # I want this to come as 'tar.gz'
print re.compile(r'^.*[.](?P<ext>tar\.gz|tar\.bz2|\w+)$').match('a.tar.bz2')group('ext')
>>> bz2           # I want this to come 'tar.bz2'

I am using (?P<ext>...) in my pattern matching as I also want to get the extension.

Please help.

Upvotes: 8

Views: 24115

Answers (6)

themachinist
themachinist

Reputation: 1433

this is simple and works on both single and multiple extensions

In [1]: '/folder/folder/folder/filename.tar.gz'.split('/')[-1].split('.')[0]
Out[1]: 'filename'

In [2]: '/folder/folder/folder/filename.tar'.split('/')[-1].split('.')[0]
Out[2]: 'filename'

In [3]: 'filename.tar.gz'.split('/')[-1].split('.')[0]
Out[3]: 'filename'

Upvotes: 2

John Lang
John Lang

Reputation: 11

Continuing from phihags answer to generic remove all double or triple extensions such as CropQDS275.jpg.aux.xml use while '.' in: 

tempfilename, file_extension = os.path.splitext(filename)
while '.' in tempfilename:
     tempfilename, tempfile_extension = os.path.splitext(tempfilename)
     file_extension = tempfile_extension + file_extension

Upvotes: 1

Izz ad-Din Ruhulessin
Izz ad-Din Ruhulessin

Reputation: 6175

Starting from phihags answer:

DOUBLE_EXTENSIONS = ['tar.gz','tar.bz2'] # Add extra extensions where desired.

def guess_extension(filename):
    """
    Guess the extension of given filename.
    """
    root,ext = os.path.splitext(filename)
    if any([filename.endswith(x) for x in DOUBLE_EXTENSIONS]):
        root, first_ext = os.path.splitext(root)
        ext = first_ext + ext
    return root, ext

Upvotes: 3

Kracekumar
Kracekumar

Reputation: 20419

I have idea which is much easier than breaking your head with regex,sometime it might sound stupid too.
name="filename.tar.gz"
extensions=('.tar.gz','.py')
[x for x in extensions if name.endswith(x)]

Upvotes: 3

Omri Barel
Omri Barel

Reputation: 9480

>>> print re.compile(r'^.*[.](?P<ext>tar\.gz|tar\.bz2|\w+)$').match('a.tar.gz').group('ext')
gz
>>> print re.compile(r'^.*?[.](?P<ext>tar\.gz|tar\.bz2|\w+)$').match('a.tar.gz').group('ext')
tar.gz
>>>

The ? operator tries to find the minimal match, so instead of .* eating ".tar" as well, .*? finds the minimal match that allows .tar.gz to be matched.

Upvotes: 5

phihag
phihag

Reputation: 287755

root,ext = os.path.splitext('a.tar.gz')
if ext in ['.gz', '.bz2']:
   ext = os.path.splitext(root)[1] + ext

Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.

Upvotes: 21

Related Questions