if_else_while_for

 import getpass
 #标准库里要加密密码需要导包getpass.但是getpass在pycharm中不好用,需要在命令窗口中输入才管用.

 _username = "abc"
 _password = "abc123"
 username = input("username:")
 # password = getpass.getpass("password:")
 password = input("password:")

 if _username==username and _password==password:
     print("Welcome user {name} login...".format(name=username))
 else:
     print("invalid username or password")

 age_of_oldboy = 56

 guess_age = int(input("guess age:"))

 if guess_age==age_of_oldboy:
     print("yes, you got it.")
 elif guess_age>age_of_oldboy:
     print("think smaller")
 else:
     print("think bigger")

 age_of_oldboy = 56

 count=0
 while True:
     if count==3:
         break
     # print("count:",count)
     guess_age = int(input("guess age:"))

     if guess_age==age_of_oldboy:
         print("yes, you got it.")
         break
     elif guess_age>age_of_oldboy:
         print("think smaller")
     else:
         print("think bigger")
     count=count+1  #count+=1
 if count==3:
     print("you have tried too many times! Fuck off!")

 # 优化后的代码
 while count<3:
     guess_age = int(input("guess age:"))

     if guess_age==age_of_oldboy:
         print("yes, you got it.")
         break
     elif guess_age>age_of_oldboy:
         print("think smaller")
     else:
         print("think bigger")
     count=count+1  #count+=1
 else:
     print("you have tried too many times! Fuck off!")

 '''
 while循环实现
 age_of_oldboy = 56

 count=0
 while True:
     if count==3:
         break
     # print("count:",count)
     guess_age = int(input("guess age:"))

     if guess_age==age_of_oldboy:
         print("yes, you got it.")
         break
     elif guess_age>age_of_oldboy:
         print("think smaller")
     else:
         print("think bigger")
     count=count+1  #count+=1
 if count==3:
     print("you have tried too many times! Fuck off!")

 # 优化后的代码
 while count<3:
     guess_age = int(input("guess age:"))

     if guess_age==age_of_oldboy:
         print("yes, you got it.")
         break
     elif guess_age>age_of_oldboy:
         print("think smaller")
     else:
         print("think bigger")
     count=count+1  #count+=1
 else:
     print("you have tried too many times! Fuck off!")

 '''
 '''
 for i in range(10):   #range10其实是从0到9.
     print("loop", i)
 '''

 # for循环来实现
 age_of_oldboy = 56
 for i in range(3):
     guess_age = int(input("guess age:"))
     if guess_age == age_of_oldboy:
         print("yes, you got it")
         break
     elif guess_age > age_of_oldboy:
         print("think smaller")
     else:
         print("think bigger")
 else:
     print("you have tried too many times.. fuck off!")

 # 0到9的数字,隔一个打印一个到控制台
 for i in range(0,10,2):   #括号中的2是步长,不写的话默认是1.若想隔两个打印一uqw,则步长设置为3即可.即for i in range(0,10,3)
     print("loop", i)

 # 每错三次不直接跳出,而是问玩家是否要继续
 age_of_oldboy = 56

 count=0
 while True:
     if count==3:
         break
     # print("count:",count)
     guess_age = int(input("guess age:"))

     if guess_age==age_of_oldboy:
         print("yes, you got it.")
         break
     elif guess_age>age_of_oldboy:
         print("think smaller")
     else:
         print("think bigger")
     count=count+1  #count+=1
     if count==3:
         continue_confirm = input('do you want to continue?')
         if continue_confirm !='n':
             count=0
 else:
     print("you have tried too many times! Fuck off!")

 # continue的用法: 跳出本次循环,继续下一次循环
 for i in range(0,10):
     if i<5:
         print("loop", i)
     else:
         continue  #跳出本次循环,继续下一次循环
     print("hehe...")

 #break:结束当前循环
 for i in range(10):
     print("-----------------",i)
     for j in range(10):
         print(j)
         if j>5:
             break