#"""学习和测试条件控制(单独使用和嵌套使用)"""

#在prompt和jupyter中多行注释都无效

#测试单独使用

name = input("place input you name : ")#默认传入的是string

mid = input("place input you age : ")

if mid.isdigit(): #判断是否为数字

age = int(mid) #转换为int ,否则直接使用if age <= 18:报错，报错信息：TypeError: '<=' not supported between instances of 'str' and 'int'

else:

while not mid.isdigit(): #在条件满足时一直执行while内部的代码块，直到条件不满足时跳出循环，执行下面的代码

mid = input("place input you age : ")

age = int(mid)

if(name == "zhangsan"): #带括号不报错，不建议使用

　　print("Hello " + name)

if name == "zhangsan":

　　print("Hello " + name)

elif name == "":

　　name = input("place again input you name : ") #单独使用弊端：不能二次验证

print("Hello " + name)

else:

　　print("who you are !")

#测试嵌套

if name == "zhangsan":

if age <= 18:

　　print(name + "is a children !")

elif age >= 60:

　　print("time is flying !")

　　age = age - 60;

print("Hello " + name + " you age is back to " + str(age)) #上面已经转为int，不能进行直接字符串拼接，报错信息：TypeError: must be str, not int

elif name == "":

　　name = input("place again input you name : ")

while name == "": #在条件满足时一直执行while内部的代码块，直到条件不满足时跳出循环，执行下面的代码

　　name = input("you input is null,place again input you name : ")

print("Hello " + name)

else:

　　print("who you are !")

结果：