Python KeyError: Understanding and Handling Key Errors in Dictionaries

A KeyError is a Python exception that is raised when attempting to access a key that does not exist in a dictionary. This error typically occurs when using the indexing syntax to retrieve a value from a dictionary using a key that is not present.

For example, consider the following code:

student_grades = {'John': 90, 'Emily': 87, 'Sam': 92}
print(student_grades['Alex'])

In this case, the key 'Alex' does not exist in the dictionary student_grades, so a KeyError will be raised. The error message will indicate that the key 'Alex' was not found in the dictionary.