Appending turns my list to NoneType

user_460847 0
Viewed 72068

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?

mutators python
4 Answers

Sometimes this error appears when you forgot to return a function at the end of another function and passed an empty list, interpreted as NoneType.

from this:

def func1():
  ...
  func2(empty_list)

def func2(list):
  ...
  # use list here but it interpreted as NoneType

to this:

def func1():
  ...
  return func2(empty_list)
    
def func2(list):
  ...
  # use list here, it will be interpreted as an empty List
user_62093550
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