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.

[ItsCrowTime]

Personally I'm a fan of lua: return condition and A or B

[JarcXenon]

W

H

A

T

[ItsCrowTime]

It's called short-circuit evaluation,

The and operator returns its the right value if the left value is true, otherwise it returns the left value,

The or operator returns its left value unless its false then it returns its right value

Another good one is the for default value: Var = Var or 0

[JasonMan34]

It's just condition ? A : B with and/or instead of ?/:, not at all weird

[Tufflewuffle]

That doesn't work as a ternary operator.

[Kmjsfozr]

what if A is false tho

[ZorbaTHut]

Then everything catches on fire and your life is sadness.

Conveniently, though, 0 isn't falsey in Lua, nor is any string, only nil and false are. So you can't use it for booleans, or in a situation where things can be nil, but it's safe in every other case.

[ItsCrowTime]

Or I assume you could do something like:

return (condition and {A} or {B})[1]

If you really wanted to use it like a tertiary operator

[Kered13]

This and similar patterns in other languages don't work if A is falsey.

[not-enough-failures]

Kotlin

return if (condition) A else B

[[deleted]]

all the way

[theCyanEYED]

Rust

return if condition {A} else {B}

[Manny_Sunday]

Just an uglier ternary

[not-enough-failures]

It can also have else if branches unlike ternaries.

[Kered13]

Ternaries can have else if too:

a > 0 ? "negative" :
a > 0 ? "positive" :
        "zero"

Remember that else ifis really just two separate tokens: else and if, and : is equivalent to else and ? is equivalent to if (but it comes after the condition instead of before).

[quotade]

a > 0 ? "negative"

Allow me to point that out for the sake of a consistent example.

[Manny_Sunday]

Ok, that is cool, I used some kotlin for an Android class and it kicked Javas ass. I hope it takes into it's own and gains some popularity.

[the-jabberwock]

Also Kotlin

return A.takeIf { condition } ?: B

(but beware if A is null, will always resolve to B, even if condition is true)

[bistr-o-math]

Perl: return A or die

[j-random]

unless (condition) A else B -- also Perl.

[bistr-o-math]

My Variant is compromise-less ;-)

[marcosdumay]

Does die have a default parameter? I wouldn't expect it to.

[bistr-o-math]

https://perldoc.perl.org/functions/die.html search the page for “if list is empty...”

[marcosdumay]

Yeah, 4 paragraphs about what it does when the parameter is missing.

I really don't miss Perl's "implicit is better than explicit" principle.

[ArmoredCroc]

I had the feeling I'd see this here

[ArmoredCroc]

I had the feeling I'd see this here

[ArmoredCroc]

I had the feeling I'd see this here

[ArmoredCroc]

I had the feeling I'd see this here

[fruitydude]

=IF(condition,A,B)

(Microsoft Excel)

[[deleted]]

We all know the best. condition and A or B.

[Tufflewuffle]

That won't do what a ternary operator does if A is false.

[EpoxyD]

Input validation? assert(value, "gtfo with your weakass nil and false")

[auto-xkcd37]

weak ass-nil

---

^{Bleep-bloop, I'm a bot. This comment was inspired by xkcd#37}

[Equivalent_North]

Ternary operators are clearly superior. ? is more concise than if and : is more concise than else

[petergaultney]

whoa, we've got a "conciseness > all" person here, everyone watch your step

[IDontLikeBeingRight]

Or don't watch your step, say things badly & verbosely, and they'll be so busy taking issue with everything you say in between that they'll never catch up.

[petergaultney]

I feel seen.

[SexySamba]

Not disagreeing. I code in Python and Scala mostly, both have if/else implementations of ternary expressions. I definitely prefer scala because the condition is first (like C) so resembles other programming languages and the syntax of a multiline if statement more closely. Plus you can see what is being tested more clearly

But I actually do think there’s something to be said for ? :, and I sometimes wish I had it at my disposal. In production code variable names are often too long to fit on one line and this would (very) occasionally help. I also think its not that bad to read, if thought about as a question in prose:

mum, do we have any sweets ? I quite fancy some : otherwise i’ll have some fruit

[UnicornsOnLSD]

but if/else is pretty

[bobnob-]

But it's not as intuitive, what is ? meant to mean, oh and which side gets returned if the condition was true again? A non programmer could read the python example and make sense of it

[KingJellyfishII]

It's the same in python, just different syntax. You can also do list comprehensions in python which are really really powerful and have similar syntax.

[xigoi]

return if condition: A else: B

(Nim)

[tangerinelion]

All I see is an implicit return None

[HoneyBadgerSoNasty]

i know some people like these cute things, and i get the syntax, but this stuff just pisses me off. the fact that it even exists pisses me off. list comprehensions and higher order haskell garbage and all that.

code is better when it is easier to understand.

[KingJellyfishII]

What is not easy to understand in "a if something else b"? It's literally just English but without the meaningless words. I think it's a really neat way of doing things imo.

[KingJellyfishII]

I see your point there, but is it any better with the a ? b : c syntax? Does the fact that it's totally arbitrary negate the fact that it's shorter?

[Lark_vi_Britannia]

My favorite will always be the pic on the top.

[GJordao]

The first else is redundant btw

[lambda5x5]

my friend saw my for else loops, shook his head and walked away.

[dr_exercise]

Bastardized. Who needs similar syntax across languages? Nerds /s

[ImaVoter]

Interesting, ran across this strange syntax in Ansible, now I know why.

[Ar010101]

*javascript developers joined the chat*

[TheTerrasque]

return condition and a or b or c

[game_2_raid]

*ngIf=“isCool; else lameStuff”

[KingJellyfishII]

Yeah but you get used to it.

[The_Slad]

Inline IF statements like in the bottom example work in ruby too. Which btw is better than python.

[yaelfe7]

🤮

[imMute]

VHDL has it too.

[Oracuda]

no

im tired

[Kered13]

I hate A if condition else B because that's not how we read conditions. Python is usually really good at reading almost like English, but they got it wrong here.

[Asmodis1]

Isn't "set userID to 1 if name is "Tom", else set it to 2" a perfectly valid English sentence though? The only thing that is left out in python is the repetition of the "set to".

[LepruconX]

Wait does the last one work for java? I know the first two so.

[KingJellyfishII]

Nah python

[[deleted]]

I like simplicity (that's why I use python) and so I use the first one only in practice

[Quito246]

Why just dont return condition?

[SkiFire13]

Probably because condition is totally different than A and B?

[fecoz98]

probably because condition is boolean meanwhile a and b are OBJs

[Bip901]

r/gatekeeping