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Python中for循环搭配else的陷阱

时间:2018-02-03 15:45:51      阅读:146      评论:0      收藏:0      [点我收藏+]

标签:body   代码   nat   rmi   without   and   打印   直接   immediate   

假设有如下代码:

for i in range(10):
    if i == 5:
        print found it! i = %s % i
else:
    print not found it ...

 

你期望的结果是,当找到5时打印出:

found it! i = 5

 

实际上打印出来的结果为:

found it! i = 5
not found it ...

 

显然这不是我们期望的结果。

根据官方文档说法:

>When the items are exhausted (which is immediately when the sequence is empty), the suite in the else clause, if present, is executed, and the loop terminates.

>A break statement executed in the first suite terminates the loop without executing the else clause’s suite. A continue statement executed in the first suite skips the rest of the suite and continues with the next item, or with the else clause if there was no next item.

https://docs.python.org/2/reference/compound_stmts.html#the-for-statement

 

大意是说当迭代的对象迭代完并为空时,位于else的子句将执行,而如果在for循环中含有break时则直接终止循环,并不会执行else子句。

所以正确的写法应该为:

for i in range(10):
    if i == 5:
        print found it! i = %s % i
        break
else:
    print not found it ...

 

当使用pylint检测代码时会提示 

Else clause on loop without a break statement (useless-else-on-loop)

 

所以养成使用pylint检测代码的习惯还是很有必要的,像这种逻辑错误不注意点还是很难发现的。

唔~

 

转载自: https://www.cnblogs.com/dspace/p/6622799.html

Python中for循环搭配else的陷阱

标签:body   代码   nat   rmi   without   and   打印   直接   immediate   

原文地址:https://www.cnblogs.com/neozheng/p/8408949.html

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