Question

let’s say I have the following code:

for a in object.a_really_huge_function():
    print a

In order to prevent a_really_huge_function from running multiple times, I am used to doing this in other languages:

a_list = object.a_really_huge_function()
for a in a_list:
    print a

Is that necessary in Python? Will the part after in run on every single loop?

Answer 1

The python interpreter is your friend.

>>> def some_func():
...     print 'in some_func'
...     return [1, 2, 3, 10]
... 
>>> for a in some_func():
...     print a
... 
in some_func
1
2
3
10

In short, no, it gets called once.