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pythonlistunique

Unique values in a list of lists in Python

I have a list of lists as following:

G = [[1,2,3],[2,3,5],[1,2,3],[4,5,6],[4,5,6]]

How can I find count of unique lists in G?

Solution

  • If you want the count of each sublist, the easiest way is to convert them to tuples and feed them to a Counter.

    from collections import Counter

G = [[1,2,3],[2,3,5],[1,2,3],[4,5,6],[4,5,6]]

print(Counter(map(tuple, G)))
# Counter({(1, 2, 3): 2, (4, 5, 6): 2, (2, 3, 5): 1})

    You need the conversion to tuples because lists are not hashable, and Counter uses a dictionary internally, which requires the keys to be hashable.