逻辑判断

用户输入判断：

1 _username='Lxxxl'
2 _password='asd123'
3 username=input("username:")
4 password=input("password:")
5 
6 if _username==username and _password==password:
7     print("Welcome user {name} login...".format(name=username))
8 else:
9     print("Invalid username or password!")

以上只能判断一次

while True:
    _username = 'Lxxxl'
    _password = 'asd123'
    username = input("username:")
    password = input("password:")

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

一直循环

for i in range(3):
    _username = 'Lxxxl'
    _password = 'asd123'
    username = input("username:")
    password = input("password:")

    if _username == username and _password == password:

        print("Welcome user {name} login...".format(name=username))
    else:
        print("Invalid username or password!")

循环三次，不论用户信息输入对或错

for i in range(3):
    _username = 'Lxxxl'
    _password = 'asd123'
    username = input("username:")
    password = input("password:")

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

答对结束，答错继续循环三次

1 count=0
2 while True:
3     print("count:",count)
4     count=count+1

      if count==1000:
      break

循环：数字从0开始+1 ,加到1000停止

1 Lxxxl_age=23
2 guess_age=int(input("Guess age:"))
3 if guess_age==Lxxxl_age:
4     print("Yse,you got it .")
5 elif guess_age>Lxxxl_age:
6     print("Think smaller...")
7 else:
8     print("Think bigger!")

猜年龄运行一次

 1 Lxxxl_age = 23
 2 count=0
 3 while True:
 4     if count==3:                                       
 5         break               换成  while count<3:
 6     guess_age = int(input("Guess age:"))
 7     if guess_age == Lxxxl_age:
 8 
 9         print("Yse,you got it .")
10         break
11     elif guess_age > Lxxxl_age:
12         print("Think smaller...")
13     else:
14         print("Think bigger!")
15     count+=1

  else:
      print("You have tried too many times ...fuck off")

 1 for i in range(3):
 2     Lxxxl_age = 23
 3     guess_age = int(input("Guess age:"))
 4     if guess_age == Lxxxl_age:
 5 
 6         print("Yse,you got it .")
 7         break
 8     elif guess_age > Lxxxl_age:
 9         print("Think smaller...")
10     else:
11         print("Think bigger!")

   else:
      print("You have tried too many times ...fuck off")

猜年龄运行三次如果答对结束（break要放在print后，否则直接结束，没有print）两种方法，第一种是计数,第二种属于优化。

1 for i in range(10):
2     print("loop",i)
3 
4 for i in range(0,10,2):
5     print("loop",i)

for循环第一个是默认从0开始，中间隔1个

Lxxxl_age = 23
count=0
while count<3:
     guess_age = int(input("Guess age:"))
     if guess_age == Lxxxl_age:

         print("Yse,you got it .")
         break
     elif guess_age > Lxxxl_age:
         print("Think smaller...")
     else:
         print("Think bigger!")
     count+=1
     if count==3:
         countine_confirm=input("Do you want to keep guessing..?")
         if countine_confirm!='n':
             count=0

如果猜错可以选择是否继续，输入n就会结束。

LXXXI