Question

hi i have a situation like this:

>>> def get():
...     for i in range(3):
...             yield [0]
... 

and i want to get this: [0,0,0]

my code now works in this way:

>>> r = []
>>> r.extend(i[0] for i in get())
>>> r
[0, 0, 0]

but i don’t like i[0]..
some advice?

(i’m on python3)

Answer 1

r.extend(i[0] for i in get())

This kind of imperative code (stateful, with inplace updates) is asking for trouble. That seems the canonical use for a functional flatten (concat):

from itertools import chain

def flatten(listOfLists):
    return chain.from_iterable(listOfLists)

def get():
    for i in range(3):
        yield [0]

print(list(flatten(get())))
# [0, 0, 0]