return keyword

[pyn00b]

In a Python function definition, sometimes you don't see the return keyword at all. Sometimes, you see it all by itself. And sometimes, you see it associated with a bunch of variables - like "return x, y, z".

Can someone clearly explain the differences between these 3 scenarios? What exactly is happening? What is the Python keyword "return" for?

[jlm699]

In a Python function definition, sometimes you don't see the return keyword at all. Sometimes, you see it all by itself. And sometimes, you see it associated with a bunch of variables - like "return x, y, z".

Can someone clearly explain the differences between these 3 scenarios? What exactly is happening? What is the Python keyword "return" for?

Let's say you have the following funtion:
[CODE=python]
def xfive(inp):
tmp = 5
result = tmp * inp
return result

# Call the function like this (>>> means this was done from the shell)
>>> xfive(3)
15
[/CODE]

This function takes an input, and returns a result... although it doesn't have to take an input... it could just as easily be the following:
[CODE=python]
def threexfive():
tmp = 5
result = tmp * 3
return result

# Then you would call the function like this
>>> threexfive()
15
[/CODE]

When a function doesn't have the return statement at the end, it still "returns" to the calling function, however it does no return a value.

When using a mutli-variable return such as:
[CODE=python]
def ret3(inp):
tmp = 5
tmp2 = 2
result = tmp * inp
return result, tmp2, tmp

# Call the function and receive three elements back
>>> mylist = xfive(3)
>>> mylist
[15, 2, 5]
[/CODE]

Basically, you can return any number of elements that you would like.

Does that clear it up a little bit? I suggest referring to the :Python documentation if you would like more explanation of basic programming techniques. You can find it here: http://www.python.org/doc/

Oh, and btw... if you see simply return with no variables associated it's the same thing as not having a return statement at all. It's just a matter of preference.

[hidrkannan]

[CODE=python]
def func1():
return

def func2():
return 5,6,7
def func3():
print 5

if __name__ == '__main__':
a = func1()
b = func2()
c = func3()

print type(a), a
print type(b), b
print type(c), c

[/CODE]

Above code has the 3 scenarios you have mentioned.

func3 does not have a return statement
func1 has a return statement by itself
func2 has a return statement with 3 integers returned

In python, function returns one and only object.

In the above code the returned objects are stored in the variable a, b & c.

Be default any function returns "NoneType" object which is the case for func3 & func1

In case of func2, it returns "Tuple" object. return 3,4,5 is equivalent to return (3,4,5).

SKN

[jlm699]

Additionally:
[CODE=python]
>>> a, b, c = func2()
>>> a
5
>>> b
6
>>> c
7
[/CODE]
You could assign each element of the tuple to its own variable without needing to bother with storing the entire object

[pyn00b]

Does that clear it up a little bit? I suggest referring to the :Python documentation if you would like more explanation of basic programming techniques. You can find it here: http://www.python.org/doc/

Oh, and btw... if you see simply return with no variables associated it's the same thing as not having a return statement at all. It's just a matter of preference.

Thank you! Yes, this is clearer to me now. So no return statement means that no value is returned (after reading elsewhere a little I found this means it returns a value of None). Anything more than 1 variable being returned results in a list being returned. As well, I didn't know that no return and a return without a variable are the exact same thing.

[bvdet]

..snip.. Anything more than 1 variable being returned results in a list being returned. ..snip..

Actually a tuple is returned. Tuples are similar to lists but have very distinct differences.