Python Day-构造函数,继承,超载(超载.构造.函数.继承.Python...)
构造函数是一个唯一的函数,当创建一个类的对象时,它会自动调用。
> - >创建时,它用于初始化它们。
->构造方法命名为__init __()
->用来表示当前对象
class employee:
def __init__(self, name, qual,department, year):
self.empname = name
self.dept = department
self.joining_year = year
self.qual = qual
def work(self):
print("working", self.empname, self.dept, self.joining_year)
emp1 = employee("guru", "b.com", "development", 2025)
emp2 = employee("pritha", "m.e.,", "design", 2025)
emp1.work()
>输出:working guru development 2025
>示例:2class employee:
salary = 25000
def __init__(self, name, qual,department, year):
self.empname = name
self.dept = department
self.joining_year = year
self.qual = qual
def work(self):
print("working", self.empname, self.dept, self.joining_year)
print(self.salary)
emp1 = employee("guru", "b.com", "development", 2025)
emp2 = employee("pritha", "m.e.,", "design", 2025)
emp1.work()
>输出:working guru development 2025
25000
__ dict __:__dict__是一个将所有实例属性存储为词典的对象的特殊属性。>
>示例:class employee:
salary = 25000
def __init__(self, name, qual,department, year):
self.empname = name
self.dept = department
self.joining_year = year
self.qual = qual
def work(self):
print("working", self.empname, self.dept, self.joining_year)
print(self.salary)
emp1 = employee("guru", "b.com", "development", 2025)
emp2 = employee("pritha", "m.e.,", "design", 2025)
print(employee.__dict__)
print(emp1.__dict__)
print(emp2.__dict__)
>输出:{'__module__': '__main__', 'salary': 25000, '__init__': <function employee.__init__ at 0x7265db745300>, 'work': <function employee.work at 0x7265db7acea0>, '__dict__': <attribute '__dict__' of 'employee' objects>, '__weakref__': <attribute '__weakref__' of 'employee' objects>, '__doc__': none}
{'empname': 'guru', 'dept': 'development', 'joining_year': 2025, 'qual': 'b.com'}
{'empname': 'pritha', 'dept': 'design', 'joining_year': 2025, 'qual': 'm.e.,'}
带装饰器的类方法 类方法是一种在类本身而不是实例上运行的方法。它是使用@classmethod装饰器定义的,并将cls(类参考)作为其第一个参数。
>示例:
class employee:
salary = 25000
def __init__(self, name, qual,department, year):
self.empname = name
self.dept = department
self.joining_year = year
self.qual = qual
@classmethod
def credit_salary(cls):
print("credit salary on last day of every month")
def work(self):
print("working", self.empname, self.dept, self.joining_year)
print(self.salary)
emp1 = employee("guru", "b.com", "development", 2025)
emp2 = employee("pritha", "m.e.,", "design", 2025)
employee.credit_salary()
>输出:
嵌套类:
>嵌套类(内类)是在另一类中定义的类。
>示例:1(使用外部类的实例调用内部类)
class college:
def init(self):
print("college constructor")
class dept:
def init(self):
print("dept constructor")
def work(self):
print("working")
principal = college()
hod = principal.dept()
hod.work()
>示例:2(直接使用外部类名来调用内部类)
class college:
def __init__(self):
print("college constructor")
class dept:
def __init__(self):
print("dept constructor")
def work(self):
print("working")
hod = college().dept()
hod.work()
output :(两个示例的相同输出)
college constructor
dept constructor
working
构建器过载:
- >构造函数过载是指在类中定义具有不同参数集的多个构造函数。 -> python不支持多个构造函数(
init方法)
-> python通过默认参数值和可变长度参数(*args或** kwargs)列表实现了过载。
>示例:
class supermarket:
def __init__(self,product_name, price, *discount):
self.product_name = product_name
self.price = price
self.discount = discount
def buy(self):
print(self.product_name, self.price, self.discount)class shapes:
def find_area(self, side1, side2):
print(side1 * side2)
class square(shapes):
pass
s = square()
s.find_area(5,5)
class rectangle(shapes):
pass
r = rectangle()
r.find_area(10,8)
product1 = supermarket("soap", 50, 10)
product2 = supermarket("brush", 60,20)
product1.buy()
product2.buy()
product3 = supermarket("rice", 60)
product3.buy()
>输出:soap 50 (10,)
brush 60 (20,)
rice 60 ()
遗产
- >继承使我们能够定义一个从另一类继承所有方法和属性的类。
是所继承的类,也称为基类。
- >child class是从另一个类继承的类,也称为派生类。
> python中的继承类型 python支持以下类型的继承类型:> >单继承:一个子类从单亲类继承。
多重继承:子类从多个父类继承。>多级继承:子类从父级继承,该类本身从另一个父级继承。> >层次结构继承:多个子类从同一父班继承。
>杂交继承:多种继承类型的组合。
- >示例:
-
PHP
class shapes: def find_area(self, side1, side2): print(side1 * side2) class square(shapes): pass s = square() s.find_area(5,5) class rectangle(shapes): pass r = rectangle() r.find_area(10,8)
>输出:
25
80
- >儿童类中的覆盖方法必须具有与父类中的方法相同的名称和参数。
>方法解析顺序(mro)
class father:
def work(self):
print("mechanical engineer")
class mother:
def work(self):
print("software engineer")
class child(mother, father):
def work(self):
print("business person")
child = child()
child.work()
>输出:商人 - >儿童课源于母亲和父亲。 -> python首先检查孩子。
->如果找不到该方法,它将检查母亲(首先列出的父)。
- >如果仍然找不到,它会检查父亲。
>
如果一个父类都没有方法,它将检查对象(所有python类的基类)。
运算符过载
运算符超载使我们可以重新定义用户定义对象的操作员( , - , *等)的行为。
print(100+200)
print("hi"+"hello")
print(100*3)
print("hi"*3)
>输出:
300
hihello
300
hihihi
- >操作员 用于添加两个整数以及加入两个字符串并合并两个列表。 ->这是可以实现的,因为“ ”运算符被int类和str类超载。
>示例:
class book:
def __init__(self, pages):
self.pages = pages
def __add__(self, second):
print(self.pages, second.pages)
return self.pages + second.pages
book1 = book(300)
book2 = book(200)
print(book1 + book2)
>输出:
300 200
500
class Employee:
def __init__(self, name, salary):
self.name = name
self.salary = salary
def __mul__(self,other):
return self.salary * other.days
class TimeSheet:
def __init__(self, name, days):
self.name = name
self.days = days
emp1 = Employee("Guru", 1000)
timesheet1 = TimeSheet("Guru", 25)
print("Monthly salary:",emp1 * timesheet1)
>输出:
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