Reference library

Lists & loops

Iterate, transform, and combine sequences with readable loop patterns.

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Lists & loops easy

Compare Two Lists in Python: Common, Only in First, Only in Second

A beginner-friendly helper that loops over two lists and returns items common to both, items only in the first list, and items only in the second list.

lists comparison loops
Python 
def compare_lists(list1, list2):
    common = []
    only_in_first = []
    only_in_second = []
    
    for item in list1:
        if item in list2:
            common.append(item)
        else:
            only_in_first.append(item)
    
    for item in list2:
        if item not in list1:
            only_in_second…
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