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

Greg Ewing greg.ewing at canterbury.ac.nz
Thu Sep 22 05:09:44 CEST 2005

Gary Herron wrote:

> 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.

The reason I like "a if b else c" is because it has the
most natural word order. In English,

   My dog is happy if he has a bone, else sad.

sounds much more natural than

   My dog is, if he has a bone, happy, else sad.

In return statements,

   return self.arg if self.arg is not None else default

looks quite all right to me. I think the fact that it does
resemble English word order so much prevents the word-soup
problem from occurring.

Interestingly, it looks *more* odd to me if parens are

   return (self.arg if self.arg is not None else default)

I think this is because, without the parens, I tend to read
the "if" as applying to the whole phrase "return self.arg",
not just to the "self.arg".

The English analogy is rewriting "My dog is happy if he has
a bone" as "If he has a bone, my dog is happy", which also
sounds natural, whereas "My dog is, if he has a bone, happy"
sounds unnatural.

So I still prefer "a if b else c" to any of the alternatives,
and I still think parens should not be required.

Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | A citizen of NewZealandCorp, a	  |
Christchurch, New Zealand	   | wholly-owned subsidiary of USA Inc.  |
greg.ewing at canterbury.ac.nz	   +--------------------------------------+

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