Abstrakta basklasser

Objektorienterad programmering i Python – fortsättningskurs

Jake Roach

Data Engineer

Abstrakta basklasser

Abstrakta basklasser skapar en mall för klasser genom att definiera abstrakta metoder som alla underklasser måste implementera

Säkerställer gemensamt beteende för en grupp klasser
Dekoratorn @abstractmethod
Avsedda att ärvas, inte instansieras
Inte alla metoder i en abstrakt basklass behöver vara abstrakta (konkreta metoder)

class School:
    # Do things such as enroll 
    # and add a course

class MiddleSchool:
    # Play an instrument, join a club
    # but must enroll and add courses

class HighSchool:
    # Play a varsity sport, apply
    # for college, but must enroll 
    # and add courses

Skapa en abstrakt basklass

from abc import ABC, abstractmethod


# Create an abstract base class that inherits
# from ABC
class School(ABC):
    @abstractmethod
    def enroll(self):
        # This method must be implemented
        # in classes that inherit from it
        pass


    # Concrete methods are inherited
    def graduate(self):
        print("Congrats on graduating!")

Ärver från klassen ABC i modulen abc
pass
Alla klasser som ärver School måste implementera metoden enroll()
Kan även implementera konkreta metoder

Implementera abstrakta basklasser

class HighSchool(School):
    def enroll(self):
        print("Welcome to high school!")

# Create an instance of HighSchool
high_school = HighSchool()
high_school.enroll()

Welcome to high school!

high_school.graduate()

Congrats on graduating!

HighSchool måste definiera en enroll()-metod
TypeError om enroll() inte är definierad
HighSchool ärver metoden graduate()

Flera abstrakta metoder

class School(ABC):
    @abstractmethod
    def enroll(self):
        pass

    @abstractmethod
    def add_course(self, course_name):
        pass

    def graduate(self):
        print("Congrats on graduating!")

Två abstrakta metoder: enroll() och add_course()

class HighSchool(School):
    def __init__(self):
        self.courses = []

    # Implementing abstract method
    def enroll(self):
        print("Welcome to high school!")

    # Implementing abstract method
    def add_course(self, course_name):
        self.courses.append(course_name)
        print(f"You enrolled in {course_name}")

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Objektorienterad programmering i Python – fortsättningskurs