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pythonlistrangeinteger

converting a list of integers into range in python


Is there something existing in python that can convert an increasing list of integers into a range list

E.g. given the set {0, 1, 2, 3, 4, 7, 8, 9, 11} I want to get { {0,4}, {7,9}, {11,11} }.

I can write a program to do this, but want to know if there is an inbuilt function in python


Solution

  • Using itertools.groupby() produces a concise but tricky implementation:

    import itertools
    
    def ranges(i):
        for a, b in itertools.groupby(enumerate(i), lambda pair: pair[1] - pair[0]):
            b = list(b)
            yield b[0][1], b[-1][1]
    
    print(list(ranges([0, 1, 2, 3, 4, 7, 8, 9, 11])))
    

    Output:

    [(0, 4), (7, 9), (11, 11)]