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[snippsat]

Also it's not necessary to append to a list.
When have done if check in function then it's not needed to add != False: outside.

def is_prime_v1(n):
    if n == 1:
        return False
    for d in range(2, n):
        if n % d == 0:
            return False
    return True

for i in range(1, 21):
    if is_prime_v1(i):
        print(i)

Output:
2
3
5
7
11
13
17
19