Another alternative: you can check if an item is in a list with if item in list:, but this is order O (n). If you are dealing with big lists of items and all you need to know is whether something is a …

Apr 22, 2013 · I have taken two actions on this question: I modified the question to clarify what is the evident original point of the question: determine if any value in one list is in another list. I …

Sep 27, 2011 · The original question was: What is the fastest way to know if a value exists in a list (a list with millions of values in it) and what its index is? Thus there are two things to find: is an …

Oct 17, 2012 · Given a list xs and a value item, how can I check whether xs contains item (i.e., if any of the elements of xs is equal to item)? Is there something like xs.contains(item)? For …

This means that python has to do a linear scan of your list, visiting each element and comparing it against the search item. If you're doing this repeatedly, or if the lists are large, this operation …

ValueError: 2 is not in list If this is a concern, either explicitly check first using item in my_list, or handle the exception with try / except as appropriate. The explicit check is simple and …

I used a defaultdict with int to indicate negative results and used the item in the first list as the key for the second list (converted to defaultdict). Because you have instant lookup with dict, you …

Jun 14, 2019 · Python's boolean operators return the last thing evaluated, not a strict True / False / None result. Similarly, option 1 is dangerous, because if mylist[-1] is falsy (numerically zero, …

Use list comprehensions if you want a single line solution. The following code returns a list containing the url_string when it has the extensions .doc, .pdf and .xls or returns empty list …

See How do Python's any and all functions work? for an explanation of all and its counterpart, any. If the condition you want to check is "is found in another container", see How to check if …