[Python-Dev] Adding a conditional expression in Py3.0 (original) (raw)

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 included:

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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