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The class null is a subclass of the symbol class, because nil is a symbol. Since nil also represents the empty list, null is a subclass of the list class, too. Methods parameters specialized to symbol or list will thus take a nil argument. Of course, a null specialization can still be defined which is a more specific match for nil.
In programming languages (especially functional programming languages) and type theory, an option type or maybe type is a polymorphic type that represents encapsulation of an optional value; e.g., it is used as the return type of functions which may or may not return a meaningful value when they are applied.
Python allows the creation of class methods and static methods via the use of the @classmethod and @staticmethod decorators. The first argument to a class method is the class object instead of the self-reference to the instance. A static method has no special first argument. Neither the instance, nor the class object is passed to a static method.
The class defines the data format or type (including member variables and their types) and available procedures (class methods or member functions) for a given type or class of object. Objects are created by calling a special type of method in the class known as a constructor. Classes may inherit from other classes, so they are arranged in a ...
A method returns to the code that invoked it when it completes all the statements in the method, reaches a return statement, or throws an exception, whichever occurs first. You declare a method's return type in its method declaration. Within the body of the method, you use the return statement to return the value.
The Python programming language has a pass statement which has no effect when executed and thus serves as a NOP. It is primarily used to ensure correct syntax due to Python's indentation-sensitive syntax ; for example the syntax for definition of a class requires an indented block with the class logic, which has to be expressed as pass when it ...
Using a factory method to create instances of a class (factory method pattern) Storing the instances in a map, and returning the same instance to each request for an instance with same parameters (multiton pattern) Using lazy initialization to instantiate the object the first time it is requested (lazy initialization pattern)
In some languages, notably those influenced by Modula-3 (including Python and Go), modules are objects, and scope resolution within modules is a special case of usual object member access, so the usual method operator . is used for scope resolution.