How to fix TypeError: cannot unpack non-iterable NoneType object

While working with Python sequences such as a List or a Tuple, you might get the following error:

TypeError: cannot unpack non-iterable NoneType object

This error usually occurs when you assign an object of None value to a set of variables using the unpacking syntax.

There are two common scenarios when this error occurs:

1. You unintentionally unpack a None object
2. Forgetting the return statement in your function

The following tutorial shows an example that causes this error and how to fix it.

1. You unintentionally unpack a None object

In Python, you can set the items in a sequence to multiple variables based on the index position of those items:

fruits = ["Grape", "Apple", "Mango"]

fruit_1, fruit_2, fruit_3  = fruits

print(fruit_1)  # Grape
print(fruit_2)  # Apple
print(fruit_3)  # Mango

As you can see, each variable gets the value defined in the fruits list.

The error occurs when you assign the variables to a None value as follows:

fruit_1, fruit_2, fruit_3  = None

Output:

Traceback (most recent call last):
  File "main.py", line 1, in <module>
    fruit_1, fruit_2, fruit_3  = None
TypeError: cannot unpack non-iterable NoneType object

To resolve this error, you need to make sure that you’re not unpacking a None object.

You can do this by using an if statement to check that the variable you want to unpack is not None:

fruits = ["Grape", "Apple", "Mango"]

if fruits is not None:
    fruit_1, fruit_2, fruit_3  = fruits
else:
    print("The variable is None")

By using an if statement as shown above, Python only unpacks the variable fruits when it’s not a None object.

Sometimes, you also get this error when you unintentionally unpack a variable that has a None value.

For example, you unpack the variable that gets assigned the return value of the sort() method like this:

fruits = ["Grape", "Apple", "Mango"]

fruits = fruits.sort()

fruit_1, fruit_2, fruit_3  = fruits  # ❌

The error occurs because the sort() method modifies the original list without returning anything. When you assign the return of sort() to a variable, that variable gets assigned a None value.

To resolve the error, you need to call sort() without assigning the return value to a variable as follows:

fruits = ["Grape", "Apple", "Mango"]

fruits.sort()

fruit_1, fruit_2, fruit_3  = fruits  # ✅

print(fruit_1)  # Apple
print(fruit_2)  # Grape
print(fruit_3)  # Mango

Note that this time We don’t receive any error message because the unpack works as expected.

2. Forgetting the return statement in your function

Suppose you have a function that returns a list as follows:

def get_list():
    my_list = [1, 2, 3]

Then, you try to unpack the object returned when you call the function as shown below:

a, b, c = get_list()

Because you don’t have a return statement in your function, you’ll get this error:

Traceback (most recent call last):
  File "main.py", line 4, in <module>
    a, b, c = get_list()
TypeError: cannot unpack non-iterable NoneType object

A Python function returns None by default when it has no return statement, and that’s why this error occurs.

To fix this error, you need to define a return statement in the function as follows:

def get_list():
    my_list = [1, 2, 3]
    return my_list

a, b, c = get_list()

print(a, b, c)  # 1 2 3

The error is now resolved and we can run the code just fine.

I hope this tutorial helps. See you in other articles! 👋