【Pyhthon开发】：初识Python

一、变量

声明变量

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 21:21 # example20.py # PyCharm  name = "caidongsheng"

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
以下关键字不能声明为变量名。['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'with', 'yield']

变量的赋值

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 21:21 # example20.py # PyCharm  name = "caidongsheng" name2 = name print(name,name2) ## caidongsheng caidongsheng name = "lixue" print("name2 is ",name2) ##name2 is caidongsheng

二、流程控制

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 21:21 # example20.py # PyCharm   # 提示输入用户名和密码 # 验证用户名和密码 #     如果错误，则输出用户名或密码错误 #     如果成功，则输出 欢迎，XXX!   import getpass  name = input('请输入用户名：')     ##input输入获取的值都为字符串！！！ pwd = getpass.getpass('请输入密码：')  if name == "caidongsheng" and pwd == "cmd":     print("欢迎，caidongsheng") else:     print("用户名和密码错误")

三、while循环

语法规则

while 条件:  # 循环体 # 如果条件为真，那么循环体则执行 # 如果条件为假，那么循环体不执行

break

　　break用于退出所有循环

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 21:37 # example21.py # PyCharm  while True:     print("123")     break     print("456")   输出结果： 123

continue

　　continue用于退出当前循环，继续下一次循环

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 21:37 # example21.py # PyCharm  while True:     print("123")     continue     print("456")  输出结果： 123 123 ...

四、练习题

1、使用while循环输入 1 2 3 4 5 6 8 9 10

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 10:07 # example19.py # PyCharm  num = 1 while num <= 10:     if num == 7:         pass     else:         print(num)     num += 1

2、求1-100的所有数的和

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 10:07 # example19.py # PyCharm   sum = 0  i = 1 while  i <= 100:     sum = sum + i     i = i + 1  print(sum)

3、输出 1-100 内的所有奇数

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 10:07 # example19.py # PyCharm   sum01 = 0 j = 1 while  j <= 100:     if j % 2 == 1:         sum01 = sum01 + j     else:         pass     j = j + 1  print("1到100,奇数和是： ",sum01)

4、输出 1-100 内的所有偶数

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 10:07 # example19.py # PyCharm   sum02 = 0 j1 = 1 while  j1 <= 100:     if j1 % 2 == 0:         sum02 = sum02 + j1     else:         pass     j1 = j1 + 1  print("1到100,偶数和是： ",sum02)

5、求1-2+3-4+5 ... 99的所有数的和

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 10:07 # example19.py # PyCharm   sum03 = 0 sum04 = 0  j2 = 1  while  j2 <= 99:     if j2 % 2 == 0:         sum03 = sum03 - j2     else:         sum04 = sum04 + j2     j2 = j2 + 1  print("和是： ",sum04+sum03)

6、用户登陆（三次机会重试）

#!/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7     # -*- coding:utf-8 -*-      # caidongsheng # 2019-09-08 10:07 # example19.py # PyCharm user_name = input("请输入用户名：")

loop = 1while loop <= 3:    user_name = input("请输入用户名：")    user_pass = input("请输入密码： ")    if user_name == "caidongsheng" and user_pass =="123456":        print("欢迎进入！！")        break    else:        print("用户或者密码错误！！")    loop = loop + 1

来源：博客园

作者：阳春没有雪

链接：https://www.cnblogs.com/caidongsheng94/p/11488745.html

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