On: Python indentation: very nice explanation for the curious or skeptical

[andyn]

Python 2.5 now lets you do:

 x = f(x) if a else g(y)

f() and g() aren't evaluated till they're needed.

[brlewis → andyn]

That syntax looks like it's intended to communicate that f(x) is the normal result, and g(y) is exceptional. I wouldn't want to use it unless that's what I intended to communicate. It also looks like you would need to put parens around the "if" expression if you were to use it within a more complex expression, e.g

 2 + (f(x) if a else g(y)) + 3

[nostrademons → andyn]

And before Python 2.5, people usually used this idiom:

    x = a and f(x) or g(y)

If you know the idiom, I think this is more readable (conditional is on the left), though it has the drawback of using completely nonsensical keywords.

[brlewis → nostrademons]

Another drawback I just noticed is that if f(x) returns false, you'll get g(y) even if a is true.

[brlewis → nostrademons]

I don't think the keywords are nonsensical.

   (or (and a (f x))
       (g y))

[Goladus → andyn]

Thanks, I didn't know that. That makes parenthesis optional unless you need to break precedence rules.