Why does this Python function only have one output?

Question

I have this very simple Python function, but there is one part I am confused about. The function is called bigger and it takes two numbers as inputs and outputs the bigger number. (I could only use if statements, no elses)

Here's the code:

def bigger(x, y):
    if x > y:
        return x
    return y

I would think that this code would return y if y is bigger (which it does), but it would return x and y if x is bigger (it only returns x). Why does it only return one output? Can Python functions only have one output?

It is returning y if y is bigger. – GLHF Jan 02 '15 at 00:52 — GLHF, Jan 02 '15 at 00:52
A function can only return once each time it is called. – BrenBarn Jan 02 '15 at 01:06 — BrenBarn, Jan 02 '15 at 01:06

score 4 · Answer 1 · answered Jan 02 '15 at 00:56

4

The return statement not only returns a value, but also terminates the current function and returns control to the calling function. So, this function will only return a single value. In my opinion it would be slightly more clear to write this:

def bigger(x, y):
    if x > y:
        return x
    else:
        return y

but the result would not differ.

answered Jan 02 '15 at 00:56

Andrew Gorcester

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Yes, I thought that was the misunderstanding. `return` works the same in most languages -- once you hit it, the function is over and control reverts to the function that called it. I think there are some languages where the concept of passing information back to the caller (return a value) and the concept of terminating a function (return control) are separate, but Python isn't one of them. – Andrew Gorcester Jan 02 '15 at 01:02

score 1 · Answer 2 · answered Jan 02 '15 at 00:54

1

Python functions can only return one value. It would be possible to return both x and y as a tuple, but the way this function is set up, it will return a single value and then exit the function.

answered Jan 02 '15 at 00:54

TimD1

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score 1 · Accepted Answer · answered Jan 02 '15 at 00:55

1

def bigger(x, y):
    if x > y:
        # when x>y, x will be returned and 'return y' in the last line will not be executed.
        return x
    # only if x<y, this line will be executed.
    return y

answered Jan 02 '15 at 00:55

Stephen Lin

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score 1 · Answer 4 · answered Jan 02 '15 at 00:58

In a Python function, when a return statement is encountered, execution of that function is terminated. Execution context then goes back to the context that called the function.

So, even though you see two return statements, if that first one is encountered (as a result of x being bigger than y), nothing else in the function runs.

https://docs.python.org/2/reference/simple_stmts.html#return

score 0 · Answer 5 · answered Jan 02 '15 at 00:57

Try this

def bigger(x, y):
if x > y:
    a=(x,y)
    # or a=[x,y]
    return a
return y

This way it will return x and y if x is bigger, but y if y is bigger. I assume this was your question?

The reason for this is that return gives back that 1 value, then exits the function. So it would leave the function bigger(x,y) as soon as it hits that return. If you want to return both x and y, you can do so with a tuple, list, whatever you want, as I did with a tuple.

That is true, I was just trying to make it simple/clear by assigning the value to a variable. — CyanogenCX, Jan 02 '15 at 01:07

score 0 · Answer 6 · edited Jan 02 '15 at 01:02

0

Python functions only returns one value.

You can try,

def bigger(x, y):

    #this is optional: value = None
    if x > y:
        value = x
    else:
        value = y
    return value

edited Jan 02 '15 at 01:02

CyanogenCX

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answered Jan 02 '15 at 01:00

hariK

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Why does this Python function only have one output?

6 Answers6

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