An 'IndexError' in Python occurs when you try to access an index that is out of range for a list or tuple. To fix it, ensure that your index is within the bounds of the data structure you're working with.

The 'IndexError' is a common exception that Python developers encounter, particularly when working with lists and tuples. This error occurs when you attempt to access an index that exceeds the valid range of indices for a given data structure. For example, if you have a list with three elements, trying to access the fourth element using an index of 3 will result in an IndexError, as Python uses zero-based indexing. To resolve this issue, you should first review your code to determine where the error occurs and verify the length of the list or tuple using the len() function. Ensure that any indices used in your code fall within the bounds defined by this length. Implementing checks or using try-except blocks can also provide a graceful way to handle potential IndexErrors, allowing you to inform users of the issue without crashing the program. Additionally, when iterating over lists, consider using the enumerate() function, which provides both the index and value, ensuring you stay within valid bounds. By understanding the causes of IndexErrors and implementing preventive measures, you can write more robust and error-resistant Python code.