Methods

Instance Methods

  1. # instance method
  2. class Calculator:
  3.     def add(self, a, b):
  4.         return a + b
  5. calc = Calculator()
  6. calc.add(5, 3)
  7. #ans: 8

Class Methods

  1. # class method
  2. class Dog:
  3.     count = 0
  4.     def __init__(self):
  5.         Dog.count += 1
  6.     @classmethod
  7.     def get_count(cls):
  8.         return cls.count
  9. Dog().get_count()
  10. #ans: 1

Static Methods

  1. # static method
  2. class MathUtils:
  3.     @staticmethod
  4.     def add(a, b):
  5.         return a + b
  6. MathUtils.add(5, 3)
  7. #ans: 8 (no instance needed)

Method with Self

  1. # self accesses instance
  2. class Person:
  3.     def __init__(self, name):
  4.         self.name = name
  5.     def greet(self):
  6.         return f"Hi, I'm {self.name}"
  7. Person("Alice").greet()
  8. #ans: "Hi, I'm Alice"

Exercises - Part 1

  1. # classmethod vs instance?
  2. class MyClass:
  3.     @classmethod
  4.     def method(cls):
  5.         return cls
  6. MyClass.method()
  7. #ans: <class 'MyClass'>

Exercises - Part 2

  1. # staticmethod access?
  2. class MyClass:
  3.     x = 5
  4.     @staticmethod
  5.     def method():
  6.         return x
  7. MyClass.method()
  8. #ans: NameError (no self or cls)

Exercises - Part 3

  1. # classmethod receives?
  2. class MyClass:
  3.     @classmethod
  4.     def method(cls):
  5.         return type(cls)
  6. MyClass.method()
  7. #ans: <class 'type'>

Exercises - Part 4

  1. # call instance method on class?
  2. class MyClass:
  3.     def method(self):
  4.         pass
  5. MyClass.method()
  6. #ans: TypeError (missing self)

Exercises - Part 5

  1. # staticmethod with self?
  2. class MyClass:
  3.     @staticmethod
  4.     def method(self):
  5.         pass
  6. obj = MyClass()
  7. obj.method()
  8. #ans: TypeError (no implicit self)

Exercises - Part 6

  1. # classmethod inheritance?
  2. class Base:
  3.     @classmethod
  4.     def who(cls):
  5.         return cls.__name__
  6. class Derived(Base):
  7.     pass
  8. Derived.who()
  9. #ans: "Derived"

Exercises - Part 7

  1. # method chaining?
  2. class Builder:
  3.     def set_x(self, x):
  4.         self.x = x
  5.         return self
  6.     def set_y(self, y):
  7.         self.y = y
  8.         return self
  9. Builder().set_x(1).set_y(2)

Exercises - Part 8

  1. # private method?
  2. class MyClass:
  3.     def __private(self):
  4.         pass
  5. obj = MyClass()
  6. obj.__private()
  7. #ans: AttributeError (name mangling)

Exercises - Part 9

  1. # method vs function?
  2. class MyClass:
  3.     def method(self):
  4.         pass
  5. type(MyClass.method)
  6. #ans: <class 'function'>
  7. type(MyClass().method)
  8. #ans: <class 'method'>

Exercises - Part 10

  1. # alternative constructor?
  2. class Point:
  3.     def __init__(self, x, y):
  4.         self.x = x
  5.         self.y = y
  6.     @classmethod
  7.     def origin(cls):
  8.         return cls(0, 0)
  9. Point.origin()

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