How to resolve AttributeError: ‘NoneType’ object has no attribute ‘append’ in Python

AttributeError: 'NoneType' object has no attribute 'append'

If you are looking for a solution to the error AttributeError: ‘NoneType’ object has no attribute ‘append’, here are the causes of the error and some ways you can use it to fix it. Details are below.

What causes the AttributeError: ‘NoneType’ object has no attribute ‘append’ in Python?

AttributeError is one of the exceptions in Python. AttributeError occurs when you access an undefined attribute on an object.

The error happens because you call the append() method on the value None.

Example

valueList = None

# The append() method adds an element to the end of the list
valueList.append('learnshareit')
print(valueList)

Output:

Traceback (most recent call last):
 File "./prog.py", line 4, in <module>
AttributeError: 'NoneType' object has no attribute 'append'

The same error occurs when you initialize a function that returns None.

Example:

def NoneFunc():
    return None

noneFunction = NoneFunc()
noneFunction.append('Learnshareit')
print(noneFunction)

Output:

Traceback (most recent call last):
 File "./prog.py", line 5, in <module>
AttributeError: 'NoneType' object has no attribute 'append'

Even if you declare a function that returns no value gives the same error.

Example:

def noValueFunc():
  print(['visit'])   

noValue = noValueFunc()
noValue.append('Learnshareit')
print(noValue)

Output:

Traceback (most recent call last):
 File "./prog.py", line 5, in <module>
AttributeError: 'NoneType' object has no attribute 'append'

How to solve the AttributeError: ‘NoneType’ object has no attribute ‘append’ in Python?

Check the NoneType object.

You can use the Authentication operator to check if a variable can validly call append().

Example:

  • Declare a variable whose value is None.
  • Use the Authentication operator. If the variable contains the value None, execute the if statement otherwise, the variable can use the append() attribute because it does not contain the value None.
  • You can replace the ‘is’ operator with the ‘is not’ operator (substitute statements accordingly).
valueList = []

# Use the 'is' operator
if valueList is None:
    print('Object is None')
else:
    print('Object is not None')
    valueList.append('learnshareit')    
    
print(valueList)

Output:

Object is not None
['learnshareit']

You can use the relational operator ‘!=’ for error handling.

The ‘!=’ operator compares the values ​​of the arguments: if they are different, it returns True. If equal, returns False.

Example:

valueList = []

# Use the relational operator '!='
if valueList != None:
    print('Object is not None')
    valueList.append('learnshareit')
else:
     print('Object is None')
    
print(valueList)

Output:

Object is not None
['learnshareit']

Use the try/except block check for the occurrence of None.

Example:

valueList = []

try:
    valueList.append('learnshareit')
except AttributeError:
    print('Object is None')
     
print(valueList)

Output:

['learnshareit']

Avoid initializing functions that do not return results or return None.

To solve the error in this case, you need to change the function’s return value (see the two examples that cause the above error) to a list that can be an empty list or a list with elements already present.

Example:

def ValueFunc():
    # The return value is an empty list. This will not cause an error
    return []

myValue = ValueFunc()

# Add the element to that list
myValue.append('Learnshareit')
print(myValue)

Output:

['learnshareit']

Summary

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