How to append to the end of an empty list?

Question

I have a list:

list1=[] 

the length of the list is undetermined so I am trying to append objects to the end of list1 like such:

for i in range(0, n):      list1=list1.append([i]) 

But my output keeps giving this error: AttributeError: 'NoneType' object has no attribute 'append'

Is this because list1 starts off as an empty list? How do I fix this error?

Answer 1

append actually changes the list. Also, it takes an item, not a list. Hence, all you need is

for i in range(n):    list1.append(i) 

(By the way, note that you can use range(n), in this case.)

I assume your actual use is more complicated, but you may be able to use a list comprehension, which is more pythonic for this:

list1 = [i for i in range(n)] 

Or, in this case, in Python 2.x range(n) in fact creates the list that you want already, although in Python 3.x, you need list(range(n)).

Answer 2

You don't need the assignment operator. append returns None.