Python can the line "return x if y" be used?

Question

In this answer it is stated that you can use return A+1 if A > B else A-1in python 3, yet when i try to use it:

def max3(a,b,c):
    return a if a > b and c
    return b if b > c else c

i get an invalid syntax error. I've tried looking online but I can't find anything on this, if anyone could help I'd appreciate it.

thanks.

@rdas functions can have many return statements without code blocks but only the first one can take effect — Yang HG, May 21 '20 at 10:49

user2390182 · Accepted Answer · 2020-05-21T11:02:45.680

1

You can nest the conditional expression:

def max3(a,b,c):
    return a if a > b and a > c else b if b > c else c

Just make sure to always have an else part, otherwise the expression won't know what to evaluate to. Whether this is the most readable solution is at best questionable. There is no price for fewest lines/bytes (unless you are playing code golf).

Also note that a > b and c is not the same as a > b and a > c. You can shorten that to b < a > c, but then readability will take another hit.

edited May 21 '20 at 11:02

answered May 21 '20 at 10:43

user2390182

72,016
6
67
89

Of course this quickly becomes unintelligible, so… please don't and use some other approach. – deceze May 21 '20 at 10:46
I agree, the question is, however, purely academical to begin with. And this demonstrates the workings of the `a if b else c` syntax. – user2390182 May 21 '20 at 10:48
If we discuss academically, please do not call this syntax an "operator". – Marcin Orlowski May 21 '20 at 10:56
@MarcinOrlowski Even the official python docs refer to the [conditional expression](https://docs.python.org/3/reference/expressions.html#conditional-expressions) as the "ternary operator". – user2390182 May 21 '20 at 10:57
Still, it's not an operator. – Marcin Orlowski May 21 '20 at 10:58

score 1 · Answer 2 · answered May 21 '20 at 10:52

The second return statement in the function will not have any effect and the function will return whatever is returned by the first return statement. In the first return statement there must be an else otherwise it will be an syntax error. So, it should be

return a if a>b else b

To evaluate max in 3 ints

return a if a > b and a > c else b if b > c else c

score -1 · Answer 3 · answered May 23 '20 at 18:30

-1

def max3(a,b,c): if a > b and a > c: return a elif b > c else a > c: return b

use colons at the end of a conditional statement.

using an "else:" part is not compulsory.

answered May 23 '20 at 18:30

Stack3002

4
6

the line " elif b > c and a > c: return b" must be on other line. – Stack3002 May 23 '20 at 18:32
in my answer all the lines got into one line. – Stack3002 May 23 '20 at 18:33
write return statement after the conditional statement. Please upvote my answer. – Stack3002 May 23 '20 at 18:34

Python can the line "return x if y" be used?

3 Answers3

use colons at the end of a conditional statement.

using an "else:" part is not compulsory.