What operator is used to check if a value exists in a list?

• A. in
• B. has
• C. exists
• D. contains

Answer: (A)

The operator used to check if a value exists in a list is "in." This operator allows you to evaluate whether a specified value is present within a list or other iterable objects like strings or tuples. When you use this operator, the expression will return a Boolean value: it will return True if the value is found, and False if it is not.

For example, if you have a list called my_list and you want to check if the number 3 is in that list, you would use the syntax 3 in my_list. This will yield True if 3 is an element of my_list, demonstrating the efficient membership test that the "in" operator provides in Python.