python class 정리 🐍

Judy·2023년 6월 21일

dev python

Python 🐍

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2/3

Why?

OOP (Object Oriented Programming)

For Object Oriented Programming
It helps to structure and modularize your code to improve maintainability and make your code more reusable

How?

Instance & Method

Data : Instance
Function : Method

Create instance & call method

class Person:
    # Initialize instance(object)
    def __init__(self):
    	# Create attribute
        # Assign value to 'self.attribute' in '__init__' method 
        self.hello = 'Hello'
 
    def greeting(self):
        # Using attributes inside a class
        print(self.hello)
 
# Instanse = class()
# Create an instance to use the class
james = Person()
# Call method
james.greeting()    # "Hello"

Get parameter when creating instance

class Person:
    def __init__(self, name, age, address):
        self.hello = '안녕하세요.'
        self.name = name
        self.age = age
        self.address = address
 
    def greeting(self):
        print('{0} 저는 {1}입니다.'.format(self.hello, self.name))
 
maria = Person('마리아', 20, '서울시 서초구 반포동')
maria.greeting()    # 안녕하세요. 저는 마리아입니다.
 
print('이름:', maria.name)       # 마리아
print('나이:', maria.age)        # 20
print('주소:', maria.address)    # 서울시 서초구 반포동

Inheritance

Get inheritance

class Person:

    def __init__(self):
        self.name = 'judy.'

    def greeting(self):
        print(f'안녕하세요. 저는 {self.name} 입니다.')
 
# Inherit class 'Person'
class Student(Person):
    def study(self):
        print('공부하기')
 
james = Student()
james.greeting()    # 안녕하세요.
james.study()       # 공부하기

Private attribute & method

Private attribute that is not accessible from outside the class and can only be used inside the class.
Used when it is an important value and should not be changed outside

class Person:
    def __init__(self, name, age, address, wallet):
        self.name = name
        self.age = age
        self.address = address
        self.__wallet = wallet    # '__value' : private
 
    def pay(self, amount):
        self.__wallet -= amount   # Only can access to private attribute with method in class
        print('이제 {0}원 남았네요.'.format(self.__wallet))

    def __greeting(self):   # '__function' : private
        print('Hello')
 
    def hello(self):
        self.__greeting()    # Can call private method in class
 
 
maria = Person('마리아', 20, '서울시 서초구 반포동', 10000)

# Error : AttributeError: 'Person' object has no attribute '__wallet'
# Accessing private properties/methods is not allowed from outside the class
maria.__wallet -= 10000
maria.__greeting()

# Accessible using methods created within the class
maria.pay(3000)