call_count.py

#!/usr/bin/env python3.7


def read_stdin() -> list:
    """
    Returns a list of str read from stdin.
    Use whitespaces as word separator.
    """
    # 0 is the file descriptor of stdin.
    # A more clever way would have been to use sys.stdin, but it is forbidden for pedagogic reasons
    with open(0) as stdin:
        # Cannot use readline because stdin is stored in live memory and is forgotten once it is read.
        # So if you use readline against it, you will read only the first line
        return stdin.read().split()


def parse_start_end_time_stamps(time_stamps: list):
    """
    Get list of str which represents a pair of semi-colon separated time-stamps
    Returns a generator which yields pairs of start & end time-stamps
    """
    for line in time_stamps:
        yield [int(time_stamp) for time_stamp in line.split(":")]


def count_second_usage_nbr(time_stamps) -> dict:
    """
    Counts the number of times a specific second has been spent in a call.
    Returns a dict with time-stamps as keys and the number of time each time-stamp has been spent in a call as value
    """
    call_summary = {}
    for boundaries in time_stamps:
        for time_stamp in range(*boundaries):  # Assumes that start is inclusive & end is exclusive
            if time_stamp in call_summary:
                call_summary[time_stamp] += 1
            else:
                call_summary[time_stamp] = 1
    return call_summary


def main():
    print(max(count_second_usage_nbr(parse_start_end_time_stamps(read_stdin())).values()))


def test():
    generator = parse_start_end_time_stamps(["14:42", "0:100"])
    assert next(generator) == [14, 42]
    assert next(generator) == [0, 100]

    assert count_second_usage_nbr(((1, 2), (0, 3), (1, 4))) == {0: 1, 1: 3, 2: 2, 3: 1}


if __name__ == '__main__':
    main()