PEP308: Yet another syntax proposal

holger krekel pyth at devel.trillke.net
Mon Feb 10 18:32:08 CET 2003


Harvey Thomas wrote:
> Unless I'm missing the point completely, compare:
> 
> if cond:
>     x = calc(1, resource_intensive_1())
> else:
>     x = calc(1, resource_intensive_2())
> 
> with
> 
> x = calc(1, iif(cond, resource_intensive_1(), resource_intensive_2()))
> 
> In the second case both resource_intensive_1() and resource_intensive_2()
> are evaluated. There is of course the possibility of undesired side-effects.

I don't mind having to write the 4-liner if i execute
"resource_intensive" functions.  I would say that *especially* when
you have "huge" functions with side effects you should choose the 4-liner
over an expression.   Often the two functions will have different
arguments where you need to adapt to.   Adding this logic to the 
already-too-long expressions becomes a pain to maintain and read.  

far more often a ternary op is used to switch between two strings
or two numbers aka

    result = input=='y' and "yes" or "no"

and has the net side effect that people (must) understand in their
learning process how and & or works in Python.  Calling different
methods hints at conditional control-flow and that is better done 
with an easy-to read if-statement which supports you by
indentation i.e. visual clues. 

    holger





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