محاسبه اعداد اول در پایتون

def isprime(n):
    if n == 1:
        return False
    for x in range(2, n):
        if n % x == 0:
            return False
    else:
        return True

def primes(n = 1):
    while(True):
        if isprime(n): yield n
        n += 1

while True:
    try:
        usr = int(input('Enter your number : '))
        for a in primes():
            if a > usr: break
            print(a)
        break
    except ValueError:
        print('Oops! Your input is wrong...')