In Python, what is a dictionary that uses strings as keys, and what is the difference between direct lookup and checking if a key exists?

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In Python, a dictionary that uses strings as keys is a data structure that stores key-value pairs where the keys are strings and the values can be of any data type.

Direct lookup is a process of accessing the value associated with a specific key in a dictionary. It involves simply providing the key as an index to the dictionary, which returns the corresponding value.

Checking if a key exists in a dictionary is a process of verifying whether a given key exists in the dictionary or not. This is done using the 'in' operator, which returns a Boolean value indicating whether the key exists in the dictionary or not.

The difference between direct lookup and checking if a key exists is that direct lookup returns the value associated with a key if it exists, while checking if a key exists only returns a Boolean indicating the existence of the key.