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Drew Hoover
2,952 PointsMy solution works with using + list concatenation, but not by using .extend().
The following will pass the test case:
def first_and_last_4(iterable):
return iterable[:4] + iterable[-4:]
#The following will return None:
def first_and_last_4(iterable):
return iterable[:4].extend(iterable[-4:])
Why?
[markdown added by mod]
1 Answer
Chris Freeman
Treehouse Moderator 68,423 PointsThe extend() list method does not return a value. Instead, it modifies a list "in place".
iterable[4:] creates a temporary local variable, then extend() add more elements. In the end there is no return value other than None
You can create a local variable, extend it, then return it:
#The following will return None:
def first_and_last_4(iterable):
result = iterable[:4]
result.extend(iterable[-4:])
return result
Note that strings are iterables that do not have the extend() method. So this will fail on strings.