A curious bit of code...

[Mark Lawrence]

On 14/02/2014 20:04, forman.simon at gmail.com wrote:
> On Thursday, February 13, 2014 7:26:48 PM UTC-8, Ned Batchelder wrote:
>> On 2/13/14 9:45 PM, forman.simon at gmail.com wrote:
>>
>>> For the record I wasn't worried about the performance.  ;-)
>>
>>>
>>
>>> It was for Tkinter event strings not markup tags.
>>
>>>
>>
>>> I'm glad this was the time winner!
>>
>>>
>>
>>> "key and key[0] == '<' and key[-1] == '>'"
>>
>>>
>>
>>>
>>
>>> Cheers to the folks who did the timings (and saved me from the trouble!)
>>
>>>
>>
>>> Last but not least...  s[::len(s)-1]   omg!!?   ;-D
>>
>>>
>>
>>
>>
>> If you aren't worried about performance, why are you choosing your code
>>
>> based on which is the fastest?  There are other characteristics
>>
>> (clarity, flexibility, robustness, ...) that could be more useful.
>
>
> I guess I'm taking the word "worried" a little too seriously.
>
> Back story: I am hoping to contribute to IDLE and am reading the code as a first step.  I came across that line of code (BTW, I was wrong: it is NOT processing Tkinter event strings but rather special "<pyshell#...> entries" in linecache.cache [1]) and had to resist the urge to change it to something more readable (to me.)  But when I thought about it I wasn't able to discern if any of the new versions would actually be enough of an improvement to justify changing it.
>
> To be clear: I have no intention of modifying the IDLE codebase just for fairly trivial points like this one line.
>
> The most satisfying (to me) of the possibilities is "if key and key[0] == '<' and key[-1] == '>':" in the dimensions, if you will, of readability and, uh, unsurprising-ness, and so I was pleased to learn that that was also the fastest.
>
>
> (FWIW, it seems to me that whoever wrote that line was influenced by shell programming.  It's a shell sort of a trick to my eye.)
>
>
> When writing Python code I *do* value "clarity, flexibility, robustness" and almost never worry about performance unless something is actually slow in a way that affects something..
>
> Warm regards,
> ~Simon
>
>
> [1] http://hg.python.org/cpython/file/3a1db0d2747e/Lib/idlelib/PyShell.py#l117
>

Pleased to have you on board, as I'm know that Terry Reedy et al can do 
with a helping hand.

But please note you appear to be using google groups, hence the double 
line spacing above and trying to reply to paragraphs that run as a 
single line across the screen.  Therefore would you please read and 
action this https://wiki.python.org/moin/GoogleGroupsPython, thanks.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

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