Python TypeError: cannot unpack non-iterable NoneType object Solution

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Python TypeError: cannot unpack non-iterable NoneType object Solution
vinaykhatri

Vinay Khatri
Last updated on April 25, 2024

    In Python, we can unpack iterable objects and assign their element value to multiple variables. But if we try to unpack a NoneType object value None , we will encounter the "TypeError: cannot unpack non-iterable NoneType object" Error.

    In this Python guide, we will discuss this error in detail and learn how to fix it. We will also walk through an example scenario, so you can figure out how to solve this error for yourself.

    Python Problem: Python Program to Swap Two Variables

    In Python unpacking, we can assign iterable object's (string, tuple, list, set, and dictionary) items to the multiple variables using a single-line statement.

    For example

    # list object
    my_list= [20, 30, 40]
    
    # unpacking
    x, y, z = my_list

    The above code will unpack the list my_list and assign the values 20 to x, 30 to y, and 40 to z.

    The unpacking can only be performed using an iterable object. And if we try to perform it on a None value, we will receive the error TypeError: cannot unpack non-iterable NoneType object . The Error statement "TypeError: cannot unpack non-iterable NoneType object" has two parts.

    1. TypeError.
    2. cannot unpack non-iterable NoneType object

    1. TypeError

    TypeError is a Python standard exception. This exception is raised in a Python program when performing an invalid or unsupported operation on a Python object. When we perform unpacking on a None value, we receive a TypeError exception.

    2. cannot unpack non-iterable NoneType object

    This is the error message that tags along with the Python TypeError exception. The error message is clearly telling us that we are trying to unpack a non-iterable NoneType object , which is not supported in Python. You will only encounter this error in your Python program when you try to unpack a None value.

    Example

    # None unpacking
    a, b, c = None

    Output

    Traceback (most recent call last):
      File "main.py", line 2, in 
        a, b, c = None
    TypeError: cannot unpack non-iterable NoneType object

    Common Example Scenario

    Encountering this error is common when you are trying to unpack an iterable object, and for some reason, you declare that iterable object as a None value.

    Example

    Let's say you have a list prices that contains three price ranges for a similar product. And need to write a program that sorts the prices list and assigns the three prices to the expensive , medium and cheap variables.

    # list
    prices = [100, 50, 200]
    
    # sort the list
    prices = prices.sort()
    
    # unpack
    cheap, medium, expensive = prices
    print("Expensive: ", expensive)
    print("Medium: ", medium)
    print("Cheap: ", cheap)

    Output

    Traceback (most recent call last):
      File "main.py", line 8, in 
        expensive, medium, cheap = prices
    TypeError: cannot unpack non-iterable NoneType object

    Break the code In the above example, we are receiving an error in line 8 with expensive, medium, cheap = prices . This is because at that statement, the value of prices in None .

    In line 5, we are sorting the list with statement prices = prices.sort() . The list sort() method sorts the list in place and returns None. At that point, the value of prices became None and when we tried to unpack it, we received the "TypeError: cannot unpack non-iterable NoneType object" Error.

    Solution

    To solve the above problem, we need to make sure that we are not assigning any None value to the list prices .

    # list
    prices = [100, 50, 200]
    
    # sort the list
    prices.sort()
    
    # unpack
    cheap, medium, expensive = prices
    
    print("Expensive: ", expensive)
    print("Medium: ", medium)
    print("Cheap: ", cheap)

    Output

    Expensive: 200
    Medium: 100
    Cheap: 50

    Wrapping Up!

    In this Python tutorial, we learned why "TypeError: cannot unpack non-iterable NoneType object" is raised in a Python program. The NoneType object value None is not iterable , and when we try to unpack it, we encounter this error. To fix this error, you need to make sure that you are not unpacking the None value in your program. A common case when you encounter this error is when you unpack a return value from a method or function that returns None.

    So be careful with the value you are receiving. If you are still getting this error in your Python program, you can share your code and query in the comment section. We will try to help you in debugging.

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