Python Guide Package statement execution

Today in the project encountered a problem, in the First_page reference login method, the first login can log in normally, after successful login, then choose to return to the main menu, back to the previous page, and then select the login times wrong "Login_class isnotdefined"

Best of all, and later found to be Python's Guide package mechanism problem, import statement only in the execution of this module alone will be actively executed, the other class in the method call it will not execute import statement, so after entering the login and then choose Back to the home page, no execution of the Guide package statement, so will error " Login_class is not defined ", so adding an absolute path before the login () method avoids this error.

Python Guide Package statement execution