python - 定义的 Python 变量

Question

考虑示例 1：

numbers = [ 1,2,4,5,7,8,3]
for val in numbers:
    sum = 0
    sum = sum + val
print("The sum is: ",sum)

上述代码的输出是：3

示例 2：

numbers = [ 1,2,4,5,7,8,3]
sum =0
for val in numbers:
     sum = sum + val
print("The sum is: ",sum)

此代码的输出为：30

在 for 循环外和 for 循环内定义 sum 有什么区别？

标签： python

Answer 1

循环内求和：如果在循环内标定 sum=0，它将获取并打印数组 numbers = [ 1,2,4,5,7,8,3] for val in numbers 的最后一个值： sum = 0 sum = sum + 值

print(sum) 3 sum outside loop：它将每次从您的循环值中分配总和值，总和值全局存储并根据您的 for 循环数一次又一次地递增 = [ 1,2,4,5,7,8, 3] sum=0 for val in numbers：sum = sum + val

打印（总和）30