else 是否在 for 循环之外，如果是，为什么 else 不执行？

Question

numbers = [10, 20, 33, 55, 39, 55, 75, 37, 21, 23, 41, 13]

for num in numbers:
    if num % 2 == 0:
       print(num)
       break
else:
   print(num)

在上面的代码中，我确实有 else 块对应于 for 循环并且没有被执行。有人可以指导我为什么它不执行吗？

Answer 1

没有其他 "if"。我想你需要这样的东西：

numbers = [10, 20, 33, 55, 39, 55, 75, 37, 21, 23, 41, 13]

for num in numbers:
    if num % 2 == 0:
        print(num)
        break
print(num)

Answer 2

缩进好像不对，试试这个

for num in numbers:
    if num % 2 == 0:
        print(num)
        break
    else:
        print(num)

Answer 3

是的，else 块对应于 for 循环，但它只会在 break 永远不会执行的情况下执行。由于您在 numbers 列表中有偶数，因此执行中断，这就是为什么 else 未执行

for num in numbers:
  if num % 2 == 0:
     print(num)
     break
else:
  print(num)

尝试使用此列表 number=[11,22,33]，else 块将被执行，以获取更多信息 4.4. break and continue Statements, and else Clauses on Loops

Python 有不同的语法，其中循环语句可能有一个 else 子句

Loop statements may have an else clause; it is executed when the loop terminates through exhaustion of the iterable (with for) or when the condition becomes false (with while), but not when the loop is terminated by a break statement. This is exemplified by the following loop, which searches for prime numbers:

Answer 4

我认为最好用不同的测试来证明这一点。所以一个 for 循环可以有一个 else 块。 else 块只有在循环正常完成时才会执行。即循环中没有 break 。如果我们创建一个接受列表和分隔符的函数。我们可以看到，如果 if 条件匹配并且我们打印然后 break，else 块永远不会是运行。只有当我们运行在没有 break 的情况下一直执行循环时，才会执行 else

def is_divisable_by(nums, divider):
    for num in nums:
        if num % divider == 0:
            print(num, "is divsiable by ", divider)
            break
    else:
        print("none of the numbers", nums, "were divisable by", divider)

numbers = [1, 6, 3]
numbers2 = [7, 8, 10]
is_divisable_by(numbers, 2)
is_divisable_by(numbers, 7)
is_divisable_by(numbers2, 4)
is_divisable_by(numbers2, 6)

输出

6 is divsiable by  2
none of the numbers [1, 6, 3] were divisable by 7
8 is divsiable by  4
none of the numbers [7, 8, 10] were divisable by 6

else 是否在 for 循环之外，如果是，为什么 else 不执行？

Is else outside for loop, if yes why else is not executing?

python

loops

for-loop

indentation