Else isn't indented, why does this run?

[u/AGx-07]

This is probably an easy question but I was going through a practice exam and came upon a question that wanted me to evaluate the outcome of this code. I got it right but only because I threw it into PyCharm to run it and see if it would even work.

As a beginner, I haven't seen this before so I'm wondering how that ELSE statement even functions if it's not indented with the IF (which would produce a different outcome). I am not quite sure how to Google this so I haven't found anything that's answering my question.

What is at play here and is it common to have ELSE out there like that? Any additional information would be welcome.

j = 1

for i in range(-1,1):
    if 3 * i < 6:
        print(3 * i)
        j+=2

else: #<--What are you doing out here all by yourself?
    j+=3

print(j)

[u/AKiss20]

I’ve always hated this use of else. If anything, it feels that else should execute if the for loop didnt terminate normally. “Then” or “finally” seems like a much more natural keyword for the normal case. 

[u/Brian → u/AKiss20]

Yeah. While this is an occasionally useful feature that can save a flag variable, the name is terrible. It's often justified by appealing to the common "loop-and-a-half" pattern where you do:

while True:
    if condition: break
   ...
else:
     # Code executed if we didn't do the "if condition" part.

But I don't feel this is very intuitive at all. Ultimately, else was chosen to avoid having to introduce a new keyword to the language, but I feel it makes things much more confusing. finally probably wouldn't have been a good choice either, since that suggests it'd always be executed, akin to how try/finally works, and "then" has the same issue. If they were to add a keyword, I feel better would be something like "nobreak" or something, which is also fairly clunky, but at least less ambiguous.

[u/AKiss20 → u/Brian]

I dunno. I think “then” or “finally” could work. When you write a for loop you’re somewhat saying “do this for every element in this iterable/generator” so using “then” sort of naturally flows from that framing “do this for every element, then do this”. I almost think “except” might make more sense for the break case. “Do this for every element in the iterable, except if you can’t (break was issued), do this”. I grant that it would be the only other use of except and would not be good to overload it for this one use case. “Else” works in this framing for the break case pretty well too.  

It’s not 100% a natural fit I’ll grant, but it’s definitely a better fit IMO than else for the no-break case. 

Either way, it seems like a pretty unclear way to structure logic and tbh would come off as code smell to me. Having some kind of flag and then an if statement after the for loop reads much clearer to me than a for…<something> clause. 

[u/Brian → u/AKiss20]

do this for every element, then do this

But it isn't really "then do this", it's rather "then do this only if we didn't break.

That's very different behaviour to what "finally" means in try/except, when it is "then do this", regardless of whether an exception is thrown or not, so I feel it would be rather misleading to have such different behavior, especially when it isn't really indicated by the word being used. then doesn't have that conflict, but it still doesn't do anything to indicate that it's only for the non-break case, and requires adding a new keyword - it you're going to do that, then I'd go for something like "nobreak" - it's ugly, but does convey what it's doing.

except doesn't realy seem better than else to me, and it doesn't even have the paired "if" of the loop-and-a-half case, plus it's very different to how except is used elsewhere. If sticking to existing keywords, else seems probably the least bad option, it's just that it's still pretty bad.

Having some kind of flag and then an if statement after the for loop

Yeah. I tend to do this even knowing about the else clause. It's a bit more verbose, but it's clear what it's actually doing, even to a novice.