python 基础之for循环有限循环

#  range(3) 表示

>>> range(3)
[0, 1, 2]

　　for循环

for i in range(3):
    print(i)

　　测试

0
1
2

　　打印1~100的奇数

for i in range(101):
    if i % 2 == 1:
       print('chenxi:',i)

　　测试

chenxi: 1
chenxi: 3
chenxi: 5
chenxi: 7
chenxi: 9
chenxi: 11
chenxi: 13
chenxi: 15
chenxi: 17
chenxi: 19
chenxi: 21
chenxi: 23
chenxi: 25
chenxi: 27
chenxi: 29
chenxi: 31
chenxi: 33
chenxi: 35
chenxi: 37
chenxi: 39
chenxi: 41
chenxi: 43
chenxi: 45
chenxi: 47
chenxi: 49
chenxi: 51
chenxi: 53
chenxi: 55
chenxi: 57
chenxi: 59
chenxi: 61
chenxi: 63
chenxi: 65
chenxi: 67
chenxi: 69
chenxi: 71
chenxi: 73
chenxi: 75
chenxi: 77
chenxi: 79
chenxi: 81
chenxi: 83
chenxi: 85
chenxi: 87
chenxi: 89
chenxi: 91
chenxi: 93
chenxi: 95
chenxi: 97
chenxi: 99

　　另一种方式

for i in range(1,101,2):  #2步长
       print('chenxi:',i)

　　测试

D:\python\python.exe D:/untitled/dir/for.py
chenxi: 1
chenxi: 3
chenxi: 5
chenxi: 7
chenxi: 9
chenxi: 11
chenxi: 13
chenxi: 15
chenxi: 17
chenxi: 19
chenxi: 21
chenxi: 23
chenxi: 25
chenxi: 27
chenxi: 29
chenxi: 31
chenxi: 33
chenxi: 35
chenxi: 37
chenxi: 39
chenxi: 41
chenxi: 43
chenxi: 45
chenxi: 47
chenxi: 49
chenxi: 51
chenxi: 53
chenxi: 55
chenxi: 57
chenxi: 59
chenxi: 61
chenxi: 63
chenxi: 65
chenxi: 67
chenxi: 69
chenxi: 71
chenxi: 73
chenxi: 75
chenxi: 77
chenxi: 79
chenxi: 81
chenxi: 83
chenxi: 85
chenxi: 87
chenxi: 89
chenxi: 91
chenxi: 93
chenxi: 95
chenxi: 97
chenxi: 99

Process finished with exit code 0

　　用逻辑与条件判断，打印1-100，跳过50-70之间数字

for i in range(101):
    if i < 50 or i > 70:
        print(i)

　　测试

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100

　　利用for循环判断加if判断，写登录程序

# 用户登录程序判断用户名密码
username = "chenxi"
passwed = "testki"
#h = 9
for i in range(3):#重试3次
    user = input("用户名:")
    passi = input("密码：")
    if user == username and passi == passwed :
        print("登录成功")
        break #跳出循环
    else:
        if i < 2:
            print("用户名或密码错误")
        else:
            print("请重新登录")

　　测试-1

D:\python\python.exe D:/untitled/dir/for.py
用户名:jhj
密码：hghbj
用户名或密码错误
用户名:fvbn
密码：bhbnb
用户名或密码错误
用户名:gbhgjhbj
密码：jbj
请重新登录

Process finished with exit code 0

　　测试-2

D:\python\python.exe D:/untitled/dir/for.py
用户名:chenxi
密码：testki
登录成功

Process finished with exit code 0

　　利用for循环判断加if判断，写登录程序-2

username = "chenxi"
passwed = "testki"
passed_test = False
for i in range(3):
    user = input("输入用户名：")
    passw = input("请输入密码：")
    if user == username and passw == passwed:
        print("登录成功")
        passed_test = True
        break
    else:
        print("登录失败")
if not  passed_test:
    print("不要脸")

　　测试-1

D:\python\python.exe D:/untitled/dir/for.py
输入用户名：iyghgh
请输入密码：gvhvhv
登录失败
输入用户名：ghfvhvh
请输入密码：jbjbj
登录失败
输入用户名：bhgbhjbj
请输入密码：hjhjh
登录失败
不要脸

Process finished with exit code 0

　　测试-2

D:\python\python.exe D:/untitled/dir/for.py
输入用户名：chenxi
请输入密码：testki
登录成功

Process finished with exit code 0