loop to perform a random amount of times

I need to generate a random number which I'll call x, and then generate x amount of numbers that are also random. I'm trying a for loop to no avail. There's more to the assignment but I feel like I'm at a roadblock till I figure this out.

My code:

def main():
    import random
    numbers_file=open('numbers.txt','w')
    file_size = random.randint(4,7)

    for x in range(file_size):
        x = random.randint(5,19)
        numbers_file.write(str(x))



    print (file_size)   
    print (x)

main()

The print commands at the bottom are only there to test it as I need to write the random numbers to a file afterward.