python判断素数

判断是否为素数，如果是1的话输出(1不是素数，1可以被1整除)

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代码如下：

val = int(input("Enter a number: "))
flag = 0
if val == 1:
    print("%d is not prime."%val)
    print("1 is divisible by 1.")
else:
    for i in range(2,val):
        if val%i == 0:
            if flag == 0:
                print("%d is not prime."%val)
                print("%d is divisible by %d." % (val, i))
                flag = 1
            else:
                print("%d is divisible by %d."%(val,i))

    if flag == 0:
        print("%d is prime."%val)





num=int(input('Enter a number:'))
def isPrime(n): 
    if n <= 1: 
        return False
    i = 2
    while i*i <= n: 
        if n % i == 0: 
              return False
        i += 1
    return True
if num==1:
    print('1 is not prime.')
    print('1 is divisible by 1.')
else:
    if isPrime(num):
        print('%d is prime.'%num)
    else:
        print('%d is not prime.'%num)


x = int(input("Enter a number:"))
prime = 1
for i in range(2,x):
    if x%i == 0:
       prime = 0
       break
if x == 1:
    print("1 is not prime.")
    print("1 is divisible by 1.")
elif prime == 0:
    print("%d is not prime." %x)
else:
    print("%d is prime." %x)
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