What is the pythonic way of writing the following code?
extensions = ['.mp3','.avi'] file_name = 'test.mp3' for extension in extensions: if file_name.endswith(extension): #do stuff I have a vague memory that the explicit declaration of the for loop can be avoided and be written in the if condition. Is this true?
Though not widely known, str.endswith also accepts a tuple. You don't need to loop.
>>> 'test.mp3'.endswith(('.mp3', '.avi')) True 
import string; str.endswith(tuple(string.ascii_lowercase))
endswith accepts tuple only for python 2.5 and above
list, the CPython optimizer (not knowing endswith won't store/mutate them) has to rebuild the list on every call. Put them in a tuple, and the optimizer can store off the tuple at compile time and just load it from the array of constants cheaply on each call. Similar sort of nudge to the one you get from using sum on an iterable of strings; it would work either way, but the code would be slower the wrong way.Just use:
if file_name.endswith(tuple(extensions)): another way which can return the list of matching strings is
sample = "alexis has the control" matched_strings = filter(sample.endswith, ["trol", "ol", "troll"]) print matched_strings ['trol', 'ol'] 
There is two ways: regular expressions and string (str) methods.
String methods are usually faster ( ~2x ).
import re, timeit p = re.compile('.*(.mp3|.avi)$', re.IGNORECASE) file_name = 'test.mp3' print(bool(t.match(file_name)) %timeit bool(t.match(file_name) 792 ns ± 1.83 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
file_name = 'test.mp3' extensions = ('.mp3','.avi') print(file_name.lower().endswith(extensions)) %timeit file_name.lower().endswith(extensions) 274 ns ± 4.22 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
I just came across this, while looking for something else.
I would recommend to go with the methods in the os package. This is because you can make it more general, compensating for any weird case.
You can do something like:
import os the_file = 'aaaa/bbbb/ccc.ddd' extensions_list = ['ddd', 'eee', 'fff'] if os.path.splitext(the_file)[-1] in extensions_list: # Do your thing. I have this:
def has_extension(filename, extension): ext = "." + extension if filename.endswith(ext): return True else: return False 
return filename.endswith(ext) ? :PAnother possibility could be to make use of IN statement:
extensions = ['.mp3','.avi'] file_name = 'test.mp3' if "." in file_name and file_name[file_name.rindex("."):] in extensions: print(True) 
index should be rindex in that case.
if any((file_name.endswith(ext) for ext in extensions)).