反復が不可能な場合とその理由は何ですか?

TypeError: 'NoneType' Object is Not Iterable

In Python, an iterable is a data structure that can be iterated over to access its elements one by one. However, if you attempt to iterate over a value that is None, you will encounter the following error:

TypeError: 'NoneType' object is not iterable

Cause of the Error

This error occurs when you try to iterate over a variable that has the value None. None represents the absence of a value or the null value in Python. As such, it cannot be iterated over because it has no elements to iterate through.

Example

The following code demonstrates the error:

<code class="python">data = None
for row in data:  # Gives TypeError!
    print(row)</code>

In this example, the variable data is assigned the value None. When you try to iterate over data using the for loop, you will get the TypeError because None is not iterable.

Solution

To resolve this issue, ensure that the variable you intend to iterate over contains a valid non-None iterable such as a list, tuple, or dictionary. If the variable is expected to have a non-None value, you can use a conditional check to handle situations where it may be None.

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