Python - OOP(Object-Oriented Programming) Special (Magic/Dunder) Methods

** OOP(Object-Oriented Programming) Special (Magic/Dunder) Methods


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print(1 + 2)
print('a' + 'b')

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3
ab

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class Employee:

raise_amt = 1.04

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_amt)


emp_1 = Employee('HAN', 'SeokDu', 50000)
emp_2 = Employee('KIM', 'Employee', 20000)

print(emp_1)

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__main__.Employee object at 0x00C11D18

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class Employee:

raise_amt = 1.04

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

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

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

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

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

emp_1 = Employee('HAN', 'SeokDu', 50000)
emp_2 = Employee('KIM', 'Employee', 20000)

print(repr(emp_1))
print(str(emp_1))

---------------------------------

Employee('HAN', 'SeokDu', 50000)
HAN SeokDu - HAN.SeokDu@company.com

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print(1 + 2)

print(int.__add__(1,2))

print(str.__add__('a', 'b'))

print(len('test'))

print('test'.__len__())

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3
3
ab
4
4

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class Employee:

raise_amt = 1.04

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

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

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

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('HAN', 'SeokDu', 50000)
emp_2 = Employee('KIM', 'Employee', 20000)

print(emp_1 + emp_2)

---------------------------------

70000

---------------------------------

==========================================

class Employee:

raise_amt = 1.04

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

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

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

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('HAN', 'SeokDu', 50000)
emp_2 = Employee('KIM', 'Employee', 20000)

print(emp_1 + emp_2)

---------------------------------

    print(emp_1 + emp_2)
TypeError: unsupported operand type(s) for +: 'Employee' and 'Employee'

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https://docs.python.org/3.8/reference/datamodel.html?highlight=__add__#emulating-numeric-types

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class Employee:

raise_amt = 1.04

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

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

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

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('HAN', 'SeokDu', 50000)
emp_2 = Employee('KIM', 'Employee', 20000)

print(len(emp_1))

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10

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