Python coin flipper with GUI
You are abusing the heads &amp; tails lists into making simple counters.

heads = []
tails = []

for flips in range(int(guess)):
    random_number = random.randint(1, 2)
    if random_number == 1:
        heads.append("Heads")
    elif random_number == 2:
        tails.append("Tails")

len(tails)
len(heads)


This could be replaced with simply:

heads = 0
tails = 0

for flips in range(int(guess)):
    random_number = random.randint(1, 2)
    if random_number == 1:
        heads += 1
    else:
        tails += 1