12、python基础学习-for循环

 1 #__author: hlc
 2 #date: 2019/5/25
 3 
 4 # for i in range(1,100,2) : #2为步长
 5 #     print("loop:",i)
 6 
 7 # for i in range(100) :
 8 #     if i < 20 or i > 80 :
 9 #         print(i)
10 #
11 # _user = "abc"
12 # _passwd = "123"
13 #
14 # flag = False
15 # for i in range(3) :
16 #     username = input("your usernaem>>>: ")
17 #     password = input("your password>>>: ")
18 #     if username == _user and password == _passwd :
19 #         print("Welcome %s login ..." % _user)
20 #         flag = True
21 #         break #跳出 ，中断
22 #     else:
23 #         print("Invalid username or password !")
24 # if not flag :
25 #     print("错误次数过多！。。。")
26 #
27 # C:\python37\python.exe D:/python-note/for_loop.py
28 # your usernaem>>>: sdaf
29 # your password>>>: asdf
30 # Invalid username or password !
31 # your usernaem>>>: abc
32 # your password>>>: 123
33 # Welcome abc login ...
34 
35 # C:\python37\python.exe D:/python-note/for_loop.py
36 # your usernaem>>>: a
37 # your password>>>: a
38 # Invalid username or password !
39 # your usernaem>>>: a
40 # your password>>>: a
41 # Invalid username or password !
42 # your usernaem>>>: a
43 # your password>>>: a
44 # Invalid username or password !
45 # 错误次数过多！。。。
46 
47 _user = "abc"
48 _passwd = "123"
49 
50 for i in range(3) :
51     username = input("your usernaem>>>: ")
52     password = input("your password>>>: ")
53     if username == _user and password == _passwd :
54         print("Welcome %s login ..." % _user)
55         break #跳出 ，中断
56     else:
57         print("Invalid username or password !")
58 else:
59     print("错误次数过多！。。。")
60     
61 # C:\python37\python.exe D:/python-note/for_loop.py
62 # your usernaem>>>: sdf
63 # your password>>>: sadf
64 # Invalid username or password !
65 # your usernaem>>>: asdf
66 # your password>>>: asdf
67 # Invalid username or password !
68 # your usernaem>>>: asdf
69 # your password>>>: asdf
70 # Invalid username or password !
71 # 错误次数过多！。。。