Does Python have a cleaner way to express "if x contains a|b|c|d..."?

tom picture tom · Oct 31, 2013 · Viewed 17.6k times · Source

The Pythonic way to check if a string x is a substring of y is:

if x in y:

Finding if x is equivalent to a, b, c, d, e, f or g is also Pythonic:

if x in [a,b,c,d,e,f,g]:

But checking if some string x contains either a, b, c, d, e, f or g seems clunky:

if a in x or b in x or c in x or d in x or e in x or f in x or g in x

Is there a more Pythonic method of checking if a string x contains an element of a list?

I know it is trivial to write this myself using a loop or using a regex:

re.search('(dog|cat|bird|mouse|elephant|pig|cow)', x)

but I was wondering if there was a cleaner way that does not involve regex.

Answer

arshajii picture arshajii · Oct 31, 2013

The Pythonic approach would be to use any():

if any(s in x for s in (a,b,c,d,e,f,g)):

From the linked documentation:

any(iterable)

Return True if any element of the iterable is true. If the iterable is empty, return False. Equivalent to:

def any(iterable):
    for element in iterable:
        if element:
            return True
    return False

Also, notice that I've used a tuple instead of a list here. If your a-g values are pre-defined, then a tuple would indeed be preferred. See: Are tuples more efficient than lists in Python?