Classmethods

Lets say we want to have a given method that will be shared among all instances. These methods are called classmethods, the are called with the class as the first argument instead of an instance of the class.

Lets look at an example

class Human:
	# this class attribute is shared by all instances of the class
	species = "H. sapiens" 

	def __init__(self, name):
		self.name = name

	def say(self, msg):
		print(f"{self.name}: {msg}")

	@classmethod # this is called a decorator, it decorates a function or method
	def get_species(cls):
		return cls.species

i = Human(name="Ian") # just like with functions, you can have positional arguments for the __init__
i.say("Hi")            # Ian: hi
j = Human("Joel")
j.say("Hi")            # Joey: hi

i.say(i.get_species()) # Ian: H. sapiens
j.say(j.get_species()) # Joel: H. sapiens

# change the shared attribute for all classes
Human.species = "H. neanderthalensis"
i.say(i.get_species()) # Ian: H. neanderthalensis
j.say(j.get_species()) # Joel: H. neanderthalensis

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