Static method in Python

A static method is a plain function that lives inside a class. It does not get self or the class, so it cannot read or change any object. Use one when a helper belongs with the class but does not need its data.

The program

class Temperature:
    def __init__(self, celsius):
        self.celsius = celsius

    # normal method: needs an object (self)
    def describe(self):
        return f"{self.celsius} °C is {self.to_fahrenheit(self.celsius)} °F"

    # static method: no self, no cls
    @staticmethod
    def to_fahrenheit(celsius):
        return celsius * 9 / 5 + 32

    # class method: gets the class, often used as another way to create objects
    @classmethod
    def from_fahrenheit(cls, fahrenheit):
        return cls((fahrenheit - 32) * 5 / 9)


print(Temperature.to_fahrenheit(100))
print(Temperature(25).describe())

body = Temperature.from_fahrenheit(98.6)
print(round(body.celsius, 1))

212.0
25 °C is 77.0 °F
37.0

How it works

• Temperature.to_fahrenheit(100) is called on the class itself. No Temperature object is created.
• Inside describe, the same static method is called as self.to_fahrenheit(...). Both ways work.
• from_fahrenheit gets the class as cls and calls cls(...) to build a new object. This is the usual job of a class method: a second way to create objects. Because it uses cls and not Temperature, a child class that inherits it would create objects of the child class.
• round(body.celsius, 1) keeps the output short. Float results often have long decimals: Temperature.from_fahrenheit(100).celsius is 37.77777777777778.

Which one to use

If a static method is not closely tied to the class, a normal function in the module is often simpler.