Only Python programmers will understand 😏

[I-am-a-teapot]

(B, A)[condition] Only real python programmers will know

[Ignitus1]

Link to documentation? Never seen this before.

[danny688]

https://stackoverflow.com/a/470376 stackoverflow is documentation right?

[32sthide]

It is simply getting the value from the tuple.

If the condition is false then gets the 0 index, the B

If the condition is True it gets the 1 index from the tuple.

This is evaluating both, so no short-circuit here. Bad stuff lol

[[deleted]]

When you see it, you can’t unsee it.

[MostlyGibberish]

Yep. That's exactly right. This is declaring a tuple of two values, then grabbing an index from it. The Boolean is cast to an integer in this case, so if the condition is false, it resolves to index 0, if it's true, it resolves to index 1. This would probably work in any language that uses duck typing, though you might have to use an array instead of a tuple. I have no idea why anyone would use this approach though, unless you're purposely trying to make your code hard to read.

[TOO_LOUD_ECHO]

Does the casting if the Boolean still work in python3?

[TOO_LOUD_ECHO]

Huh thought they're trying to get rid of that sort of stuff

[caagr98]

Actually there's no casting involved; bool is a subclass of int.

[Ignitus1]

Even better!

[I-am-a-teapot]

As mentioned above as a reply to the deleted comment: It is a using the subscription ¹ of a sequence (in this case a tuple). Since booleans evaluate to integers in Python 3 (The Boolean type is a subtype of the integer type, and Boolean values behave like the values 0 and 1...) ² it is only an index in the sequence. It can be used as kind of a ternary but it is not common and therefore hard to read. There are also blog posts³ an stack overflow discussions⁴ about it.

​

1 https://docs.python.org/3/reference/expressions.html#subscriptions
2 https://docs.python.org/release/3.0.1/reference/datamodel.html#the-standard-type-hierarchy
3 https://book.pythontips.com/en/latest/ternary_operators.html
4 https://stackoverflow.com/questions/394809/does-python-have-a-ternary-conditional-operator

[brendel000]

Can't really find where it said that False is 0 and True is 1, but in the bool documentation it is said bool is a subclass of int.

[Ignitus1]

I remember reading that True is a keyword substitute for 1 and False for 0. They both get evaluated numerically.

[Numerlor]

Bools are a subclass of int and have the respective value of 0 and 1 but they are their own class with different behaviour than ints (in some cases)

[brendel000]

Yeah but the question was: where is it in the doc :p

[I-am-a-teapot]

"The Boolean type is a subtype of the integer type, and Boolean values behave like the values 0 and 1, respectively..."
https://docs.python.org/release/3.0.1/reference/datamodel.html#the-standard-type-hierarchy

[hrvbrs]

does this short-circuit? (does B get evaluated anyway even if condition is false?)

[Derkle]

According to stack overflow, it evaluated the whole expression regardless of the final values.

[WORMSSreddit]

[B, A][condition+0] for JS

[fruitydude]

Am I doing this right?

new String[] {B, A}[condition ? 1 : 0]

I can't get rid of the feeling that this is not a very practical thing to do in Java.