Random.randint produces same answer each run - or is my code faulty?

I want to repeat a coin flip 500 times, and repeat that experiment 30 times and print the total amount of tails (1) per total run. Just running heads/tails is easy enough, but when I mess around to try to repeat this (first while loop) i get the exact same amount of tails each run, which shouldn't be possible.

While I'm a complete newbie, I can't figure out where I did something wrong here ... thanks!

`import random
i=0
count_1=0 
rand_count=0
while rand_count<31:
    while i < 501:
        y=random.randint(0,1)
        if y ==1:
            count_1=count_1+1
        i=i+1
    rand_count=rand_count+1
    print(count_1)`