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"for/while ... break(by any means) ... else" make sense?

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  "for/while ... break(by any means) ... else" make sense? jfong@ms4.hinet.net - 2016-06-28 18:41 -0700
    Re: "for/while ... break(by any means) ... else" make sense? Steven D'Aprano <steve@pearwood.info> - 2016-06-29 12:43 +1000
      Re: "for/while ... break(by any means) ... else" make sense? jfong@ms4.hinet.net - 2016-06-29 05:01 -0700
      Re: "for/while ... break(by any means) ... else" make sense? Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-29 14:53 +0000

#110739 — "for/while ... break(by any means) ... else" make sense?

Anyone who wrote the code below must be insane:-)

    for x in range(3):
        print(x)
    else:
        print('I am done')

But here it seems perfectly OK:

    for x in range(3):
        print(x)
        if x == 1:  break
    else:
        print('I am done')

To me, the "else" was bonded with "break" (or return, or raise, or...),
not "for". It make sense:-)

--Jach

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#110743

On Wed, 29 Jun 2016 11:41 am, jfong@ms4.hinet.net wrote:

> Anyone who wrote the code below must be insane:-)
> 
>     for x in range(3):
>         print(x)
>     else:
>         print('I am done')

*shrug* Insane or not, it's legal.

import math
pass
import os
pass
import sys

is "insane" too, but still legal. The Python interpreter does not judge your
code.



> But here it seems perfectly OK:
> 
>     for x in range(3):
>         print(x)
>         if x == 1:  break
>     else:
>         print('I am done')
> 
> To me, the "else" was bonded with "break" (or return, or raise, or...),
> not "for". It make sense:-)


Just ten minutes ago I wrote code that looks like this:


for x in sequence:
    try:
        do_something(x)
    except Error:
        continue  # try again with the next item
    break
else:
    default()


The "else" in for...else has nothing to do with any "if" inside the for
block.



-- 
Steven
“Cheer up,” they said, “things could be worse.” So I cheered up, and sure
enough, things got worse.

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#110773

Steven D'Aprano at 2016/6/29 UTC+8 10:43:52AM wrote:
> The "else" in for...else has nothing to do with any "if" inside the for
> block.

Yes, the "else" has nothing to do with "break" syntactically in Python language, but semantically in English it cause confusion. When I said "insane", I just want to emphasis this situation. 

"else" should appear only when there is a "break" in the "for" block, then "for ...break... else ..." become perfectly alright semantically. Never think of it in "for ...else ..." or the confusion bond to come up:-)

--Jach

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#110782

On 2016-06-29, Steven D'Aprano <steve@pearwood.info> wrote:

[...]

> is "insane" too, but still legal. The Python interpreter does not
> judge your code.

That's what Usenet is for.

-- 
Grant Edwards               grant.b.edwards        Yow! I'm a nuclear
                                  at               submarine under the
                              gmail.com            polar ice cap and I need
                                                   a Kleenex!

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