python►b-OOP

Python-b04-Special(Magic/Dunder) Methods

This article shows the examples of special(magic/dunder) methods in python

basic

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class Employee:
    raise_amount = 2.04

    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'

    def fullname(self):
        return '{} {}'.format(self.first, self.last)

    def apply_raise(self):
        self.pay = int(self.pay * self.raise_amount)

    def set_regular_raise_amount(self, amount):
        self.raise_amount = amount

    @classmethod
    def set_class_raise_amount(cls, amount):
        cls.raise_amount = amount

    @staticmethod
    def is_workday(day):
        if day.weekday() == 5 or day.weekday() == 6:
            return False
        return True

emp_1 = Employee('Bob', 'Gobdo', 20)
print(emp_1)                # <__main__.Employee object at 0x00000200249F63A0>

__repr__ method is used for debug

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    class Employee:
    raise_amount = 2.04

    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'

    def fullname(self):
        return '{} {}'.format(self.first, self.last)

    def apply_raise(self):
        self.pay = int(self.pay * self.raise_amount)

    def set_regular_raise_amount(self, amount):
        self.raise_amount = amount

    @classmethod
    def set_class_raise_amount(cls, amount):
        cls.raise_amount = amount

    @staticmethod
    def is_workday(day):
        if day.weekday() == 5 or day.weekday() == 6:
            return False
        return True
        
    def __repr__(self):
        return "Employee('{}','{}',{})".format(self.first, self.last, self.pay)

emp_1 = Employee('Bob', 'Gobdo', 20)
print(emp_1)        #Employee('Bob','Gobdo',20)

__str__ method is used for user

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class Employee:
    raise_amount = 2.04

    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'

    def fullname(self):
        return '{} {}'.format(self.first, self.last)

    def apply_raise(self):
        self.pay = int(self.pay * self.raise_amount)

    def set_regular_raise_amount(self, amount):
        self.raise_amount = amount

    @classmethod
    def set_class_raise_amount(cls, amount):
        cls.raise_amount = amount

    @staticmethod
    def is_workday(day):
        if day.weekday() == 5 or day.weekday() == 6:
            return False
        return True

    def __repr__(self):
        return "Employee('{}','{}',{})".format(self.first, self.last, self.pay)

    def __str__(self):
        return '{} - {}'.format(self.fullname(), self.email)
    
emp_1 = Employee('Bob', 'Gobdo', 20)
print(emp_1)                # Bob Gobdo - Bob.Gobdo@company.com

print(emp_1.__repr__())     # Employee('Bob','Gobdo',20)

__add__ method

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class Employee:
    raise_amount = 2.04

    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'

    def fullname(self):
        return '{} {}'.format(self.first, self.last)

    def apply_raise(self):
        self.pay = int(self.pay * self.raise_amount)

    def set_regular_raise_amount(self, amount):
        self.raise_amount = amount

    @classmethod
    def set_class_raise_amount(cls, amount):
        cls.raise_amount = amount

    @staticmethod
    def is_workday(day):
        if day.weekday() == 5 or day.weekday() == 6:
            return False
        return True

    def __repr__(self):
        return "Employee('{}','{}',{})".format(self.first, self.last, self.pay)

    def __str__(self):
        return '{} - {}'.format(self.fullname(), self.email)

    def __add__(self, other):
        return self.pay + other.pay

emp_1 = Employee('Bob', 'Gobdo', 20)
emp_2 = Employee('John', 'Youhs', 30)
print(emp_1 + emp_2)            # 50

__len__ method

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class Employee:
    raise_amount = 2.04

    def __init__(self, first, last, pay):
        self.first = first
        self.last = last
        self.pay = pay
        self.email = first + '.' + last + '@company.com'

    def fullname(self):
        return '{} {}'.format(self.first, self.last)

    def apply_raise(self):
        self.pay = int(self.pay * self.raise_amount)

    def set_regular_raise_amount(self, amount):
        self.raise_amount = amount

    @classmethod
    def set_class_raise_amount(cls, amount):
        cls.raise_amount = amount

    @staticmethod
    def is_workday(day):
        if day.weekday() == 5 or day.weekday() == 6:
            return False
        return True

    def __repr__(self):
        return "Employee('{}','{}',{})".format(self.first, self.last, self.pay)

    def __str__(self):
        return '{} - {}'.format(self.fullname(), self.email)

    def __add__(self, other):
        return self.pay + other.pay

    def __len__(self):
        return len(self.fullname())

emp_1 = Employee('Bob', 'Gobdo', 20)
print(len(emp_1))       # 9