Python TypeError: 'NoneType' object not iterable - What's causing it?

I'm encountering an error while running my Python script and I'm having trouble understanding the issue. I keep getting the following error message: "TypeError: 'NoneType' object is not iterable". Can someone help me understand what might be causing this error and how I can resolve it?

Here is my code:

def get_input_data():
    # Some code to retrieve input data
    return input_data

def process_data(data):
    processed_items = []
    for item in data:
        processed_item = item * 2
        processed_items.append(processed_item)
    return processed_items

def main():
    input_data = get_input_data()
    processed_data = process_data(input_data)
    print(processed_data)
    # Rest of the code

if __name__ == "__main__":
    main()

When I run the script, I receive the error message pointing to the line with the for loop in the process_data function. I've verified that the data variable has a valid value assigned to it before the loop. However, when the loop tries to iterate over it and perform some processing logic (in this case, doubling each item), the error occurs.

The error you're experiencing might be due to the get_input_data() function returning None, which is causing the NoneType object is not iterable error when the process_data() function tries to iterate over it.
To resolve this issue, you can check if the input_data is None before passing it to the process_data() function. Additionally, ensure that the get_input_data() function is implemented correctly to retrieve and return the input data.

Here is how you could fix it:

def process_data(data):
    if data is None:
        return []  # Return an empty list or handle the None case appropriately
    processed_items = []
    for item in data:
        processed_item = item * 2
        processed_items.append(processed_item)
    return processed_items