[Python-Dev] Adding a conditional expression in Py3.0

[Gary Herron]

Michael Hudson wrote:

>Guido van Rossum <guido at python.org> writes:
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>  
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>>>Given the later addition of generator expressions with mandatory
>>>parentheses , the mandatory-parentheses version of a conditional expression
>>>looks less strange to me than it did then ;-).  So I could happily use it
>>>even though I may still lean toward the other option 2 version (then-else)
>>>due to  its not needing ':'s or a third elseif term for chaining.
>>>      
>>>
>>I think I'd prefer (if <expr> then <expr> else <expre>) i.e. no
>>colons. 
>>    
>>
>
>My problem with this syntax is that it can be hard to read:
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>return if self.arg is None then default else self.arg
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>looks worryingly like
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>return NAME NAME.NAME NAME NAME NAME NAME NAME NAME.NAME
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>to me.
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But that's exactly what any language looks like if you get abstract enough:

  WORD WORD WORD WORD WORD WORD WORD

And in fact, one read and understands your return statement just like an 
English sentence -- word by word from beginning to end.  This seems an 
argument FOR the syntax not against.    Moreover, if one uses the 
proposed parenthesized syntax, even the slightly odd word order of 
"return if" is mitigated.

  return (if self.arg is None then default else self.arg)

>  
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>>None of the other expression forms (list comprehensions and
>>generator expressions) involving statement keywords use colons.
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>>
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>This is also true.
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>>>*If* you want general community input, I would suggest a runoff ballot with
>>>those four choices (and a summary of pros and cons of each), or fewer if
>>>you see any as unacceptible.
>>>      
>>>
>>If there's one thing I've learned from the PEP 308 vote, it is that
>>votes for language don't work. I prefer some discussion on Python-dev
>>after which I pick one.
>>    
>>
>
>Well, this is my input (and now I'm going to try and stay out of it).
>
>Cheers,
>mwh
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