It is more efficient to use if-return-return or if-else-return?

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Suppose I have an if statement with a return. From the efficiency perspective, should I use

if(A > B):
    return A+1
return A-1

or

if(A > B):
    return A+1
else:
    return A-1

Should I prefer one or another when using a compiled language (C) or a scripted one (Python)?

Since the return statement terminates the execution of the current function, the two forms are equivalent (although the second one is arguably more readable than the first).

The efficiency of both forms is comparable, the underlying machine code has to perform a jump if the if condition is false anyway.

Note that Python supports a syntax that allows you to use only one return statement in your case:

return A+1 if A > B else A-1

Best practice on if/return, The instruction state you should use an "else if" statement to finish the section, but I else if (choice1 === "rock") { if(choice2 === "scissors") { return "rock wins"; } else Furthermore ELSE IF is more efficient because the computer only has to​  Meta Stack Overflow your communities . Sign up or log in to customize your list. more stack exchange communities company blog. By using our site, you

From Chromium's style guide:

Don't use else after return:

# Bad
if (foo)
  return 1
else
  return 2

# Good
if (foo)
  return 1
return 2

return 1 if foo else 2

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With any sensible compiler, you should observe no difference; they should be compiled to identical machine code as they're equivalent.

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I personally avoid else blocks when possible. See the Anti-if Campaign

Also, they don't charge 'extra' for the line, you know :p

"Simple is better than complex" & "Readability is king"

delta = 1 if (A > B) else -1
return A + delta

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Comments
  • In a compiled language you don't need to worry about efficiency much. The compiler sorts that out. You should write your code so you can read it. (You still have to worry about the efficiency of your algorithms, and sloppy use of types etc. will affect efficiency - you just don't have worry about your style too much.) I don't know about Python though.
  • Relying on your compiler to sort out your code is a dangerous step - and requires an infallible compiler. Better if you know whay tou want your code to do!
  • If what you are doing is defined by the spec, then i do not believe there is any reason to doubt the compiler. It will have been written be people far smarter than you, and it's far more likely that you made a mistake than them.
  • How can this be closed for opinion based? It may be an opinion after you know that there is no performance difference between the two. I did not, and I am pretty sure that a lot of people also did not.
  • While the question is quite popular, it can't be answered accurately without a specific language in mind, or otherwise, answering for every languages would be too long for this format.
  • C supports that too. return (A>B)?A+1:A-1; However there is absolutely no gain in performance from writing the code like this. All we have achieved is to make the code obfuscated, unreadable and in some cases more vulnerable to implicit type promotions.
  • @Lundin obfuscated? unreadable? Only for those who don't know the ternary operator.
  • @Lundin Following this argumentation, < is bad practice because -1 < 1u produces an unexpected result.
  • @glglgl: No, because people expect the ?: operator to behave as if-else, which isn't true. If somebody would write code like -1 < 1u, which I doubt, they would easily spot the bug. Quite a lot of people would write some version of the code I posted however. I have seen such bugs far too often in production code to trust the ?: operator. Also as a rule of thumb, if the language gives you two different ways to do the same thing, only use one of them, don't randomly pick either of the two depending on your mood.
  • @Lundin that is an argument for being careful with ?: in C, but you seem to be saying it applies to Python as well. Can you point to any examples where using the ternary in Python leads to unexpected results?
  • Thanks. +1. May I ask why don't use else after return?
  • if-else is functionally equivalent, but it's verbose. The else is unnecessary.
  • I was surprised because the first seems more clear and thus better.
  • You could make a reasonable case for either. The most important thing in this decision IMO is to be consistent within the code base.