How is a class variable defined in Python?

A class variable in Python is defined within the class body, outside of any instance methods. This placement ensures that the variable is shared among all instances of that class. Class variables are typically used to store properties that should be the same for every instance, such as a constant value or a count of how many instances have been created.

By defining a class variable this way, all instances can access and modify it, reflecting changes across the entire class. This characteristic differentiates class variables from instance variables, which are defined within instance methods and are unique to each instance of the class.

The other options do not accurately represent the definition of a class variable. Instance methods and function-local variables pertain to the scope and context of methods and functions, without the shared characteristic inherent to class variables. Method parameters serve a different purpose as they are used to pass information into methods, not to define variables that belong to the class itself.