python课堂整理1

 

1.变量

变量只能由字母、数字、下划线组成

特例：1.变量不能用数字开头

　　   2.不能是python的关键字

          3.最好不要和python内置的东西重复

让变量名有意义 些

python3的关键字如下：

False, None, True, and, as, assert, break, class, continue, def, del, elif, else, except, finally, for, from, global, if, import, in, is

lambda, nonlocal, not, or, pass, raise, return, try, while, with, yield

2.循环的例题

1.使用循环语句输出123456  89 10

n = 1
while n <=10:
    if n == 7:
        pass
    else:
        print(n)
    n = n + 1

2.求1 - 100 的所有数的和

n = 1
count = 0
while n <= 100:
    count = count + n 
    n = n +1
print(count)

3.输出1 - 100 内的所有奇数

n = 1
while n <= 100:
　　if n % 2 != 0:
　　　　print(n)
　　n = n + 1

 4.输出1 - 100 内的所有偶数

n = 1
while n <= 100:
    if n % 2 == 0:
        print(n)
    n = n + 1

5.求1-2+3-4...+99的所有数的和

n = 1
count = 0
while n <= 5:
    if n % 2 == 0:
        count = count - n
    else:
        count = count + n
    n = n + 1
print(count)

6.用户登录，三次机会重试

 下面代码是自己写的，还未听老师的修改

n = 3
id1 = "大白"
passwd = "521"
while n >= 1:
    user = input("请输入用户名：")
    userid = input("请输入密码：")
        
    if user == id1 and userid == passwd :
        print("登录成功")
    else:
        print("用户名或密码错误，请重新输入！")
    n = n - 1
print("机会用完了qaq")