The Cost of Dynamism (was Re: Pyhon 2.x or 3.x, which is faster?)

[Mark Lawrence]

On 23/03/2016 23:55, Steven D'Aprano wrote:
> On Thu, 24 Mar 2016 03:24 am, Random832 wrote:
>
>> On Wed, Mar 23, 2016, at 12:08, Mark Lawrence wrote:
>>>> And doing it 'Pythonically' can lead to suggestions such as the
>>>> following the other day:
>>>>
>>>>    c, psource = psource[0], psource[1:]
>>>>
>>>> (where psource is a very long string), which even I could tell, from
>>>> knowing what goes on behind the scenes, wasn't going to work well
>>>> (duplicating the rest of the string roughly every other character).
>>>>
>>>
>>> It would work perfectly. How would it duplicate the rest of the string
>>> roughly every other character?
>>
>> Er, I think he's suggesting that this would be in an inner loop
>> (something like while psource: c, psource = psource[0], psource[1:]).
>> What I'm not sure of is why he thinks this is pythonic.
>
> Because somebody here (Dennis) criticised his earlier code for passing "your
> entire source string along with the character from it to the function", and
> suggested splitting the string into its head and tail instead. Dennis' code
> started:
>
>          while psource:
>                  c, psource = psource[0], psource[1:]
>                  lxsymbol = disptable[min(ord(c), 256)](c, psource)
>
>
> But one positive: this conclusively proves that "Pythonic" is in the eye of
> the beholder. Dennis thinks that c, psource = psource[0], psource[1:] is
> reasonable Python code; you think it's not ("I'm not sure why [Bart] thinks
> this is pythonic").
>
> Pythonic or not, Bart is correct to be concerned about the performance,

Where and when did he ever say anything about performance with respect 
to the above piece of code?

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

Mark Lawrence