Something Wrong With My Program's Function Python .extend()

while I was creating a function for a program in python, I encountered a problem. every time I run the program, after inputting what's needed I always get an Error saying: 'Attribu

Solution 1:

.extend is in-place method, it does not return anything, it modifies your list.

see for example

>>> print [].extend([3])
None

or

>>>x = []>>>print x
[]
>>>y = x.extend([4])>>>print y
None
>>>print x
[4]

thus to solve the problem, simply change

OUT=(OUT.extend(IN))

to

OUT.extend(IN)

or to equivalent

OUT = OUT + IN