arr_to_str_intrevals.py

def get_str_of_intervals(arr: []) -> str:
    if not arr:
        return ''
    breaks = []
    arr.sort()
    start = end = arr[0]
    for i in arr[1:]:
        diff = i - end
        if diff == 1:
            end = i
        else:
            breaks.append((start, end))
            start = end = i
    breaks.append((start, end))
    return ','.join(str(s) if s == e else f'{s}-{e}' for s, e in breaks)