How to return two variables from a python function and access its values without calling it two times?

Question

Suppose I have the following function:

def f():
   return [1,2,3], [4,5,6]

I can call this function successfully like below:

a,b = f() 
print(a,b) #prints [1, 2, 3] [4, 5, 6]

But suppose that I want to have access only to the first item (1) of the first list and the first item (4) of the second list. To do that I call it like below successfully:

a,b = f()[0][0], f()[1][0]
print(a,b) #prints 1 4

I do not control function f() as it is written in a library.

Is it possible in Python to do the last operation, without calling the function two times and without using the returned a and b values?

wim · Accepted Answer · 2019-05-02 19:19:58Z

9

Using an extended unpacking assignment:

>>> def f():
...    return [1,2,3], [4,5,6]
... 
... 
>>> [a0, *rest], [b0, *rest] = f()
>>> a0, b0
(1, 4)

Using zip-splat trick:

>>> next(zip(*f()))
(1, 4)

answered May 2, 2019 at 19:19

wim

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