Data Science

Describing Static Methods

A static method is an ordinary function that just happens to live in the namespace defined by a class
It does not operate on any kind of instance
Static methods are defined using a @staticmethod decorator
Static methods can be used to define different ways of creating new instances
The following is an example of this use-case:

>>> class Date(object):
...     def __init__(self, year, month, day):
...         self.year = year
...         self.month = month
...         self.day = day
...     @staticmethod
...     def now():
...         t = time.localtime()
...         return Date(t.tm_year, t.tm_mon, t.tm_day)
...     @staticmethod
...     def tomorrow():
...         t = time.localtime(time.time()+86400)
...         return Date(t.tm_year, t.tm_mon, t.tm_day)

>>> a = Date(1967, 4, 9)
>>> b = Date.now()
>>> c = Date.tomorrow()

Describing Class Methods

A class method is a method that operates on the class itself as an object
Class methods are defined using a @classmethod decorator
Class methods are different than instance methods in that the class is passed as the first argument

Defining Types of Methods

Instance method: A method that operates on an instance belonging to a given class
Class method: A method that operates on the class itself
Static method: A method that just happens to be packaged inside a class

>>> class Foo(object):
...     def instance_method(self, arg):
...         print('instance', arg)
...     @classmethod
...     def class_method(cls, arg):
...         print('class', arg)
...     def static_method(arg):
...         print('static', arg)

>>> Foo().instance_method('!')
'instance !'
>>> Foo().class_method('!')
'class !'
>>> Foo.static_method('!')
'static !'

References

Polymorphism

Properties