How to check if a line has one of the strings in a list

Question

Possible Duplicate    Check if multiple strings exist in another string       I am trying to find out if there is a nice and clean way to test for 3 different strings   Basically I am looping trough a file using a for loop  then I have to check if it contains 1 of the 3 strings that I have set in a list   So far I have found the multiple if condition check  but it does not feel like is really elegant and efficient   for line in file     if  string1  in line or  string2  in line or  string3  in line          print  found the string    I was thinking like creating a list that contains string1  string2 and string3  and check if any of these is contained in the line  but it doesn t seems that i can just compare the list without explicitly loop trough the list  and in that case I am basically in the same conditions as in the multiple if statement that I wrote above   Is there any smart way to check against multiple strings without writing long if statements or loop trough the elements of a list

User · Answer

This still loops through the cartesian product of the two lists, but it does it one line:

>>> lines1 = ['soup', 'butter', 'venison']
>>> lines2 = ['prune', 'rye', 'turkey']
>>> search_strings = ['a', 'b', 'c']
>>> any(s in l for l in lines1 for s in search_strings)
True
>>> any(s in l for l in lines2 for s in search_strings)
False

This also have the advantage that any short-circuits, and so the looping stops as soon as a match is found. Also, this only finds the first occurrence of a string from search_strings in linesX. If you want to find multiple occurrences you could do something like this:

>>> lines3 = ['corn', 'butter', 'apples']
>>> [(s, l) for l in lines3 for s in search_strings if s in l]
[('c', 'corn'), ('b', 'butter'), ('a', 'apples')]

If you feel like coding something more complex, it seems the Aho-Corasick algorithm can test for the presence of multiple substrings in a given input string. (Thanks to Niklas B. for pointing that out.) I still think it would result in quadratic performance for your use-case since you'll still have to call it multiple times to search multiple lines. However, it would beat the above (cubic, on average) algorithm.

User · Answer

One approach is to combine the search strings into a regex pattern as in this answer

User · Answer

strings     string1    string2    string3   for line in file      if any s in line for s in strings           print  yay

[python] How to check if a line has one of the strings in a list?

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