Check if multiple strings exist in another string

How can I check if any of the strings in an array exists in another string?

Like:

a = ['a', 'b', 'c']
str = "a123"
if a in str:
  print "some of the strings found in str"
else:
  print "no strings found in str"

That code doesn't work, it's just to show what I want to achieve.

Solution 1:

You can use any:

a_string = "A string is more than its parts!"
matches = ["more", "wholesome", "milk"]

if any(x in a_string for x in matches):

Similarly to check if all the strings from the list are found, use all instead of any.

Solution 2:

any() is by far the best approach if all you want is True or False, but if you want to know specifically which string/strings match, you can use a couple things.

If you want the first match (with False as a default):

match = next((x for x in a if x in str), False)

If you want to get all matches (including duplicates):

matches = [x for x in a if x in str]

If you want to get all non-duplicate matches (disregarding order):

matches = {x for x in a if x in str}

If you want to get all non-duplicate matches in the right order:

matches = []
for x in a:
    if x in str and x not in matches:
        matches.append(x)

Solution 3:

You should be careful if the strings in a or str gets longer. The straightforward solutions take O(S*(A^2)), where S is the length of str and A is the sum of the lenghts of all strings in a. For a faster solution, look at Aho-Corasick algorithm for string matching, which runs in linear time O(S+A).