Question

In Python Shell, I entered:

aList = ['a', 'b', 'c', 'd']  
for i in aList:  
    print(i)

and got

a  
b  
c  
d  

but when I tried:

aList = ['a', 'b', 'c', 'd']  
aList = aList.append('e')  
for i in aList:  
    print(i) 

and got

Traceback (most recent call last):  
  File "<pyshell#22>", line 1, in <module>  
    for i in aList:  
TypeError: 'NoneType' object is not iterable  

Does anyone know what’s going on? How can I fix/get around it?

Answer 1

list.append is a method that modifies the existing list. It doesn’t return a new list — it returns None, like most methods that modify the list. Simply do aList.append('e') and your list will get the element appended.