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

Question

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.

Asked By: tom

||

Source

Answer 1

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?

Answered By: arshajii

Answer 2

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

I think that’s about as short & Pythonic as you can get it.

Answered By: jwodder

Answer 3

without using any but simply max

def is_in(symbol, lst):
    return max([symbol in x for x in lst]) 

print is_in('a',['ae','br','tl'])
print is_in('c',['ae','br','tl'])

gives

>>> 
True
False

Answered By: kiriloff

Answer 4

A bit late to the party, but

not frozenset(x).isdisjoint(frozenset(y))

would work, and may be faster (algorithmically, but maybe not for smaller test cases).

Answered By: Snakes and Coffee

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

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