NameError / Python中的“名称未定义”

Question

我是 Python 初学者，收到以下错误消息：NameError: name 'z' is not defined。

导致错误的代码：

num = int(input("enter the max: "))
for i in range (2, num):
    is_prime = True
    for z in range (2, i):
        if i % z ==0:
            is_prime = False
    if is_prime:
     print(z)

Answer 1

您在for z in range (2, i): 块之外使用z。 z，假设这是确定的非质数的除数，可以存储到一个变量中以将其输出到for 块之外：

num = int(input("enter the max: "))
for i in range (2, num):
    is_prime = True
    divisable_by = 0
    for z in range (2, i):
        if i % z ==0:
            is_prime = False
            divisable_by = z
    if is_prime:
        print(divisable_by)

---

使用更具描述性的变量名称，删除附加变量：

max = int(input("enter the max: "))
# print all prime numbers up to (max)
for number in range (2, max):
    divisable_by = 0
    for divisor in range (2, int(math.sqrt(number))):
        if number % divisor == 0:
            is_prime = False
            divisable_by = divisor
    if divisable_by != 0:
        print(divisable_by)

注意：将内部循环限制为 2...squareroot(number to check) 以提高性能。