什么是for / while else子句 [英] for what are for/while else clauses
问题描述
今天我翻遍了语言规范，看看为什么......其他：
对我来说。我有点失望地得知其他条款只是简单地在循环体之后执行
- 无论是否输入循环
。
那么该功能的实际用例在哪里？
我想象只有循环体才会执行else子句
没有输入，所以我可以写这个
的结果：
print r
else ：
打印没有找到，伙计！
而不是
如果len（结果） ：
for r结果
打印r
其他：
打印没有找到，伙计！ ;
等待启示，
Diez
Hi,
today I rummaged through the language spec to see whats in the for ... else:
for me. I was sort of disappointed to learn that the else clauses simply
gets executed after the loop-body - regardless of the loop beeing entered
or not.
So where is an actual use case for that feature?
I imagined that the else-clause would only be executed if the loop body
wasn''t entered, so I could write this
for r in result:
print r
else:
print "Nothing found, dude!"
instead of
if len(result):
for r in result
print r
else:
print "Nothing found, dude!"
waiting for enlightment,
Diez
推荐答案
Diez B. Roggisch写道：
Diez B. Roggisch wrote:
今天我翻遍了语言规范，看看为什么......其他：
对我来说。我有点失望地得知其他条款只是在循环体之后被执行 - 无论是否输入循环
。
Hi,
today I rummaged through the language spec to see whats in the for ... else:
for me. I was sort of disappointed to learn that the else clauses simply
gets executed after the loop-body - regardless of the loop beeing entered
or not.
我没有意识到...对于其他存在，但根据语言
引用，else子句被执行，除非循环体退出
。休息声明。
David
I didn''t realize that for...else existed, but according to the language
reference, the else clause gets executed unless the loop body exited due
to a break statement.
David
" David C 。福克斯 <哒******* @ post.harvard.edu>在消息中写道
news：nr9tb.200590
"David C. Fox" <da*******@post.harvard.edu> wrote in message
news:nr9tb.200590
Fm2.189136@attbi_s04 ...
Fm2.189136@attbi_s04...
Diez B. Roggisch写道：
Diez B. Roggisch wrote:
今天我翻遍了语言规范，看看for ...
else：对我来说。我有点失望地得知其他条款只是在循环体之后被执行 - 无论循环是否输入
。
我没有意识到这一点。 ..else存在，但根据语言
引用，else子句被执行，除非循环体退出到break语句。
Hi,
today I rummaged through the language spec to see whats in the for ... else: for me. I was sort of disappointed to learn that the else clauses simply
gets executed after the loop-body - regardless of the loop beeing entered or not.
I didn''t realize that for...else existed, but according to the language
reference, the else clause gets executed unless the loop body exited due
to a break statement.
是的。它是循环的三个终止条件之一。问题
是它的名字真的很糟糕，终止条件我最喜欢
感兴趣
捕获的是一个循环根本没有执行的地方。
John Roth
David
Yep. It''s one of the three termination conditions for a loop. The problem
is that it''s a really bad name, and the termination condition I''m most
interested
in catching is the one where the loop didn''t execute at all.
John Roth
David
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