Which error is raised when an attempt is made to access a dictionary with a key that does not exist?

Which error is raised when an attempt is made to access a dictionary with a key that does not exist?

• A. TypeError
• B. KeyError
• C. ValueError
• D. IndexError

Answer: (B)

When a key that does not exist in a dictionary is accessed, Python raises a KeyError. This error specifically indicates that the key used in the lookup operation is not present in the dictionary's set of keys. Dictionaries in Python are designed for fast access to values based on their associated keys. When you attempt to retrieve a value by a key, Python checks if the key exists. If it does not find the key, it raises a KeyError to alert the programmer that they are trying to access a value that cannot be found due to a missing key. This behavior helps developers catch issues early when they attempt to access data structures. In contrast, the other error types have different purposes. A TypeError is raised when an operation or function is applied to an object of inappropriate type. A ValueError occurs when a function receives an argument of the right type but an inappropriate value, while an IndexError pertains to accessing an index that is out of the allowed range, typically with sequences like lists or tuples, rather than dictionaries.

When a key that does not exist in a dictionary is accessed, Python raises a KeyError. This error specifically indicates that the key used in the lookup operation is not present in the dictionary's set of keys.

Dictionaries in Python are designed for fast access to values based on their associated keys. When you attempt to retrieve a value by a key, Python checks if the key exists. If it does not find the key, it raises a KeyError to alert the programmer that they are trying to access a value that cannot be found due to a missing key. This behavior helps developers catch issues early when they attempt to access data structures.

In contrast, the other error types have different purposes. A TypeError is raised when an operation or function is applied to an object of inappropriate type. A ValueError occurs when a function receives an argument of the right type but an inappropriate value, while an IndexError pertains to accessing an index that is out of the allowed range, typically with sequences like lists or tuples, rather than dictionaries.