def gen1():
    for item in range(1, 10, 2):
        yield item


def gen2():
    for item in range(2, 20, 2):
        yield item


def gen3():
    for item in range(40, 50, 2):
        yield item


def merge_generators(gen1, gen2):
    """Live coding."""
    gen1_run = True
    gen2_run = True
    stop1 = False
    stop2 = False
    while True:
        try:
            if gen1_run:
                value1 = next(gen1)
        except StopIteration:
            stop1 = True
        try:
            if gen2_run:
                value2 = next(gen2)
        except StopIteration:
            stop2 = True
        gen1_run = True
        gen2_run = True
        if stop1 and stop2:
            break
        elif stop1:
            yield value2
        elif stop2:
            yield value1
        else:
            if value1 < value2:
                yield value1
                gen2_run = False
            else:
                yield value2
                gen1_run = False


def merge_2(*generators):
    """Not live coding."""
    # Generator, Should I run?, Current value
    matrix = [
        [gen, True, None] for gen in generators
    ]
    while matrix:
        for i, row in enumerate(matrix):
            if row[1] is True:
                try:
                    row[2] = next(row[0])
                    row[1] = False
                except StopIteration:
                    matrix.pop(i)
        if matrix:
            lowest = min(matrix, key=lambda row: row[2])
            yield lowest[2]
            lowest[1] = True


def merge_3(*generators):
    """Shorter way."""
    # Generator, Should I run?, Current value
    matrix = [
        [gen, next(gen)] for gen in generators
    ]
    while matrix:
        lowest = min(matrix, key=lambda row: row[1])
        yield lowest[1]
        try:
            lowest[1] = next(lowest[0])
        except StopIteration:
            matrix = list(filter(lambda e: e != lowest, matrix))



merge_gener = merge_3(gen1(), gen2(), gen3())

print([i for i in merge_gener])