pythonmutators

Appending turns my list to NoneType

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?

Solution

  • 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.