[ Python 常見問題 ] Counting “unique pairs” of numbers into a python dictionary?

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Question
If I have a list of tuple as below:

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1. datas = [(1, 2), (1, 2, 3), (2, 3, 4)]  

How to count pair of number such as:

(1, 2) = (1, 2)
(1, 2, 3) = (1, 2), (1, 3), (2, 3)
(2, 3, 4) = (2, 3), (3, 4), (2, 4)

Then we got: {(1, 2): 2, (1, 3): 1, (2, 3): 2, (3, 4): 1, (2, 4): 1}

How-To
What you want is to count pairs that arise from combinations in your lists. You can find those with a Counter and combinations.

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1. from itertools import combinations  
2. from collections import Counter  
3.   
4. datas = [(1, 2), (1, 2, 3), (2, 3, 4)]  
5. counter = Counter()  
6.   
7. for t in datas:  
8.     counter.update(Counter(combinations(t, 2)))  
9.       
10. display(counter)  

Output:

Counter({(1, 2): 2, (1, 3): 1, (2, 3): 2, (2, 4): 1, (3, 4): 1})