How to Efficiently Check for Matching Items in Lists: Shortcut Methods

Shortcut Approaches to Check for Matching Items in a List

Traditionally, checking for the presence of specific items in a list involves creating a function that examines each item individually. However, there are several concise methods that can accomplish this task effectively.

One such method leverages list comprehensions. For example, given a list L1 and a list of items to check L2:

[i for i in L1 if i in L2]

This comprehension will return a sublist containing only the matching items, which can be evaluated as a truth value. If the sublist is empty, its evaluation results in False, otherwise it evaluates to True.

L1 = [2,3,4]
L2 = [1,2]
print(bool([i for i in L1 if i in L2]))  # True

Another approach utilizes set intersections. By converting L1 and L2 into sets (unique element collections), the intersection of these sets yields a set containing only the common elements. Similar to list comprehensions, the evaluation of an empty intersection as a truth value produces False.

S1 = set(L1)
S2 = set(L2)
print(bool(S1.intersection(S2)))  # True

These shortcut methods provide efficient and concise alternatives to function-based implementations.

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