python 基础之for循环有限循环

#  range(3) 表示

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

　　for循环

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1 2	for i in range(3):     print(i)

　　测试

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　　打印1~100的奇数

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

　　测试

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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

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

　　测试

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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

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

　　测试

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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

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# 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")<br>        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

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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

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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

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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

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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

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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