任务是：

编写一个Python程序，提示用户创建一个用户帐户，并检查所提供的用户名和密码是否合法。在

注意：密码应该以字母开头，并且只能由字母、数字和下划线符号“u”组成。长度应该在8到16之间。在

我遇到了“密码应该以字母开头，并且只包含字母、数字和下划线符号”的问题部分。(我知道这不是最优雅的代码)username=input("Please enter a username:")

usepass=input("Please enter a password:")

#username

if len(username)<6 or len(username)>12:

print("Username is incorrect length. Your username must be between 6 and 12 characters.")

if username.isalnum() == False:

print("Username must only contain letters and numbers.")

username1=username[0]

if username1.isnumeric()== True :

print ("Your username must start with a letter")

#password

if len(usepass)<8 or len(usepass)>16:

print("Password is incorrect length. Your password must be between 8 and 16 characters.")

usepass1=usepass[0]

if usepass1.isalpha()==False:

print("Your password must start with a letter")

if usepass.isalnum()==False:

print("Your password must only contain numbers, letters and underscores.")