How to check if a key exists in a dictionary in Python?

In Python, the 'in' keyword is used to check if a key exists in a dictionary. This is the recommended and most common way to determine the presence of a key in a dictionary. When you use the 'in' keyword, it will return True if the key exists in the dictionary and False otherwise.

For example, suppose you have a dictionary named my_dict and you want to check if the key 'key' exists in it. You can do so by using the following code:

if 'key' in my_dict:

This simple line of code will return True if the key 'key' exists in my_dict, and False if it does not.

Using the 'in' keyword is the correct way to perform this check in Python, especially if you are using Python 3 or later versions where the has_key() function has been removed. Therefore, it is recommended to always use the 'in' keyword when checking for the existence of keys in dictionaries.