Python学习（001）

变量定义的规则：

　　变量名只能是字母、数字或下划线的任意组合

　　变量名的第一个字符不能是数字

　　关键字不能声明为变量名

name = "Yonig"
name2 = name
print("My name is:",name)
print("My name is:",name2)

name = "DT"
print("Now name :",name)
print("Now name2:",name2)

那么本来指向Yonig，name2直接指向Yonig并不是指向name。name和name2没有关系，name只是为name2“指路”。后name指向DT，而name2依旧指向Yonig。

 

用户输入：

username = input("username:")
password = input("password:")
print(username,password)

输入密码时，如果想要不可见，要利用getpass

import getpass
password = getpass.getpass("请输入密码：")
print(password）

 

If else流程判断

Python有强制缩进！

_usrename = "in"
_password = "123"
username = input("username:")
password = input("password:")

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

 

多种情况使用elif，第二行加int是因为，输入的是字符串需要强制转换。

age = 56
guess_age = int(input("guess age:"))
if guess_age == age:
    print("right!")
elif guess_age > age:
    print("so big")
else:
    print("so small!")

 

while循环

age = 60
count = 0
while count<3:
    guess_age = int(input("guess age:"))
    if guess_age == age:
        print("right!")
        break
    elif guess_age > age:
        print("so big")
    else:
        print("so small!")
    count +=1
else:
    print("you have tried too many time..")

 

age = 60
count = 0
while count<3:
    guess_age = int(input("guess age:"))
    if guess_age == age:
        print("right!")
        break
    elif guess_age > age:
        print("so big")
    else:
        print("so small!")
    count +=1
    if count == 3:
        continue_confirm = input("do you want to keep guessint?..")
        if continue_confirm !='n': //输入n才会停止
            count = 0
else:
    print("you have tried too many time..")

 

for循环

age = 60
for i in range(3):
    guess_age = int(input("guess age:"))
    if guess_age == age:
        print("right!")
        break
    elif guess_age > age:
        print("so big")
    else:
        print("so small!")
else:
    print("you have tried too many time..")

 

for i in range(0,10,2)://0-10的范围内，隔两个输出一次
    print("loop：",i)

 

作业：编写登陆接口

　　输入用户名密码

　　认证成功后显示欢迎信息

　　输错三次后锁定

_username = 123
_password = 123
for i in range(3):
    username = int(input("username:"))
    password = int(input("passname:"))
    if username == _username and password == _password :
        print("yes")
        break
    else:
        print("try")
else:
    print("no")