python syntax for conditional is unfortunate

Neal Becker ndbecker2 at gmail.com
Wed Sep 24 03:50:23 CEST 2008


Aaron "Castironpi" Brady wrote:

> On Sep 23, 6:52 pm, Neal Becker <ndbeck... at gmail.com> wrote:
>> In hindsight, I am disappointed with the choice of conditional syntax.  I
>> know it's too late to change.  The problem is
>>
>> y = some thing or other if x else something_else
>>
>> When scanning this my eye tends to see the first phrase and only later
>> notice that it's conditioned on x (or maybe not notice at all!). 
>> Particularly if 'some thing or other' is long or complicated.
> 
> You're talking strictly about readability, which among other things is
> in the eye of the beholder, of course.  Temporary variables can clean
> up some code, even if choosing names can be a hassle and it's more
> things to keep track of.  Long lines and extra variables form a trade-
> off.  You are writing a line with a conditional expression the value
> of which depends on something.  What does it depend on, what is its
> value if that's true, and what is it if it's false?  '...if...else...'
> only takes 6 characters... maybe you want more!
> 
> If you're looking for a strictly syntactic construct, you can always
> "fire blanks", or tracers, if the analogy's more accurate.
> 
> z= conditionally( x ) if b else y
> 
> This could serve as a gentle reminder, even where 'conditionally'
> returns its argument, i.e. is the identity function.  You can always
> roll your own ternary with extra parameters too:
> 
> z= condition( b, x, y )
> 
> Just don't confuse it with threading.Condition.
> 
> Otherwise, you're stuck with old syntax markers, and unless you
> wanted:
> 
> z= if b then x else y
> 
> You're out of options.  You have to express it somehow.  Did you want
> the condition first?  Was there an alternative proposal you
> preferred?  IINM if I'm not mistaken,
> 
> z= b and x or y
> 
> works just the same so long as x evaluates to True, as it will be
> tested.
> 
> Feel free to write your own from scratch, and we'll see how close
> Python can come to resembling it.
> 
> I suppose you can compare it to someone who stops listening before the
> word 'if', and completely misunderstands your statement.  "Feed the
> dog if he's standing near the food dish" != "Feed the dog", which can
> of course lead to errors of both omission and commission (doing too
> little -or- too much).  There's no way to fix that in a guaranteed
> way, except to say, "listen to the whole statement".
> 
> And strictly sarcastically, what did you want to do with reading the
> program?  Why were you reading it?  <snicker, ducks>

I find I'm often tripped up by:

x = Y (lots of  constructor arguments....) if something ...

on first glance, I don't notice the if.

Why am I reading this?  Umm, because I wrote it.




More information about the Python-list mailing list