On Monday, October 28, 2013 6:50:19 AM UTC-3, Wolfgang Maier wrote:
> Dear all,
>
> this is a recurring programming problem that I'm just not sure how to solve
>
> optimally, so I thought I'd ask for your advice:
>
> imagine you have a flag set somewhere earlier in your code, e.g.,
>
>
>
> needs_processing = True
>
>
>
> then in a for loop you're processing the elements of an iterable, but the
>
> kind of processing depends on the flag, e.g.,:
>
>
>
> for elem in iterable:
>
> if needs_processing:
>
> pre_process(elem) # reformat elem in place
>
> print(elem)
>
>
>
> this checks the condition every time through the for loop, even though there
>
> is no chance for needs_processing to change inside the loop, which does not
>
> look very efficient. Of course, you could rewrite the above as:
>
>
>
> if needs_processing:
>
> for elem in iterable:
>
> pre_process(elem) # reformat elem in place
>
> print(elem)
>
> else:
>
> for elem in iterable:
>
> print(elem)
>
>
>
> but this means unnecessary code-duplication.
>
>
>
> You could also define functions (or class methods):
>
> def pre_process_and_print (item):
>
> pre_process(item)
>
> print(item)
>
>
>
> def raw_print (item):
>
> print(item)
>
>
>
> then:
>
> process = pre_process_and_print if needs_processing else raw_print
>
> for elem in iterable:
>
> process(elem)
>
>
>
> but while this works for the simple example here, it becomes complicated if
>
> pre_process requires more information to do its job because then you will
>
> have to start passing around (potentially lots of) arguments.
>
>
>
> So my question is: is there an agreed-upon generally best way of dealing
>
> with this?
>
>
>
> Thanks for your help,
>
> Wolfgang
Hi All,
Trying to help you out, I wonder if something like the following code will help
on what you need.
for elem in (needs_processing and iterable or []):
pre_process(elem) # reformat elem in place
print(elem)
It avoids code duplication and only process and iterates if the condition is
True.
I hope it helps, otherwise, we could keep thinking alternatives.
Regards.
Mariano.
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