for 循环实例
print 1 至 100的奇数:
#print 奇数 for i in range(1,101,2) : # 2 为步长 print("loop:",i)
打印小于50和大于70的数字:
for i in range(100): if i < 50 or i > 70: print(i)
三次输入用户信息:
_user = "eva" _passwd = "123" for i in range(3): username = input("Username:") password = input("Password:") if username == _user and password == _password: print("Welcome %s login..." %_user) break else: print("Invalid username or password!")
三次输入不成功后打印 You can't try any more!:
_user = "eva" _passwd = "123" passed_authentication = False #默认假,不成立(flag, 标志位) for i in range(3): username = input("Username:") password = input("Password:") if username == _user and password == _passwd: print("Welcome %s login..." %_user) passed_authentication = True #真,成立 break else: print("Invalid username or password!") if not passed_authentication: print("You can't try any more!")
或者执行以下代码:
_user = "eva" _passwd = "123" for i in range(3): username = input("Username:") password = input("Password:") if username == _user and password == _passwd: print("Welcome %s login..." %_user) break #break for后就不会执行最后那个else后的语句 else: print("Invalid username or password!") else: #只要上面的for循环正常执行完毕,中间没被打断,就会执行else语句 print("You can't try any more!")
或者执行以下代码:
_user = "eva" _passwd = "123" counter = 0 while counter < 3: username = input("Username:") password = input("Password:") if username == _user and password == _passwd: print("Welcome %s login..." %_user) break else: print("Invalid username or password!") counter += 1 else: print("You can't try any more!")