python 简谈2

#1.if用法if 1<100>3:    print("right")else:    print("wrong")elif #等价于else ifpass #不执行任何操作if a>b and a==d: #且if a>b or a==d: #或者break和continue功能不变colors=('red','balck')if 'red' in colors: #判断列表中是否存在'red'    print('red')null=[]if null: #判断列表是否是空，有值返回True，空的话返回False    print(1)else:    print(0)#2.字典用法d={'pen':7,'apple':3,'applepen':10} #键值对print(d['apple'])d['apple']=10 #修改值d2={'a':[1,2,3,4],'c':{'a':1,'b':2}}print(d2['c']['a']) #输出1del d['apple']for key,value in d.items: #遍历    print(key,value)for key in d.keys():    print(key)for value in d.values():    print(value)for key in sorted(d.keys()):#键排序#3.函数def function(a=20,b=20): #设置默认值    c=a+b    print(c)function(1,2)a=1000def function(b=20):    global a#全局变量    c=a+b    print(c)function(1,2)def add(a,b):    c=a+b    return c#4.类class human:    name='someone'    age=100    def my_name(self):        print(self.name)    def my_age(self):        print(self.age)    def eat(self):        print('eat')   def think(self,a,b):     print(a+b)person1=human()person1.nameperson1.eat()person1.think(2,3)class human:    def __init__(self,name,age):#双下划线，要注意        self.name=name        self.age=age    def my_name(self):        print(self.name)    def my_age(self):        print(self.age)    def eat(self):        print('eat')    def think(self,a,b):        print(a+b)person2=human('lili',29)#定义参数class human:    def __init__(self,name='li',age='20'):#预定义        self.name=name        self.age=age    def my_name(self):        print(self.name)    def my_age(self):        print(self.age)    def eat(self):        print('eat')    def think(self,a,b):        print(a+b)person2=human()class human():    def __init__(self,name='li',age=25):        self.name=name        self.age=age        print("human init")    def my_name(self):        print(self.name)    def my_age(self):        print(self.age)    def eat(self):        print('eat')    def think(self,a,b):        print(a+b)class student(human):#子类继承父类    def __init__(self,grade=1,school='mit'):        super().__init__()#父类初始化        self.grade=grade        self.school=school        self.score=100        print('student init')    def learn(self):        print('learning')    def my_school(self):        print("school:",self.school)    def think(self,a,b):    print(a*b)#子类重写父类的函数，优先stu2=student(4)