字典的循环方法一：运行速度快，效率高

d={"name":"xiangjing","age":26,"sex":"boy","email":"123456@139.com}for k in d:    value=d.get(k)     #get()方法获取字典的值    print(k,value)    运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>name xiangjingage 26sex boy

d={"name":"xiangjing","age":26,"sex":"boy"}for k in d:    print(k,d[k])  #角标索引方式获取字典的值    运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>name xiangjingage 26sex boy

d={"name":"xiangjing","age":26,"sex":"boy"}for k,v in d.items(): #效率较低，把字典转成了一个二维数组视图    print(k,v)    运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>name xiangjingage 26sex boy

d={"name":"xiangjing","age":26,"sex":"boy","email":"123456@139.com"}a="sex"if a not in d:      #等同于 if a not in d.keys()    print("%s这个key在该字典中不存在哦！"%a)else:    print("%s这个key在该字典中存在哦！"%a)    运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>sex这个key在该字典中存在哦！

# 非空即真，非0即真   简化代码的写法TrueFalsename="xiaoming"if name:    print("t")else:    print("f")        运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>t

python一切皆对象，所有对象都有一个布尔值，获取对象的布尔值：使用内置函数 bool()

2.1、布尔值为False的对象

以下对象的布尔值均为False

print(bool(False))    print(bool(0))print(bool(None))     print(bool(""))       #空字符串print(bool([]))       #空列表print(bool(list()))print(bool(()))       #空元组print(bool(tuple()))print(bool({}))       #空字典print(bool(dict()))print(bool(set()))    #空集合运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>FalseFalseFalseFalseFalseFalseFalseFalseFalseFalseFalse

print(bool(True))print(bool("hello"))print(bool(" "))      #只含有空格的字符串 布尔值也为Trueprint(bool(123))print(bool(123.55))运行后>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>TrueTrueTrueTrueTrue