Suppose I have a list of Person objects, which have an age and room_number attribute, and I have written a check() function, which returns True, if person.age() and person.room_number() are satisfactory, False otherwise.
filter(check, list_of_people_objects) would return a list of Person objects which satisfies the criteria of check()
However, my question is, is there a way of returning a list of each approved Person's room number without iterating through the list twice, like so without using list comprehension? So filtering, but returning a more specific attribute of the iterable.
map(lambda x: x.room_number(), filter(check, list_of_people_objects))
There are in fact two ways.
map(..., itertools.ifilter(..))
List comprehension
[x.room_number() for x in people if check(x)]
Which you choose is mostly a matter of taste, but convention leans towards the latter.