How to Access StringVar Data from One Tkinter Page to Another?

How to Access Variable Data from a Class

Problem Summary

You have multiple pages of widgets collecting user input in a multi-page Tkinter application. Each page is instantiated as a class in the main application, but you're facing difficulty in obtaining the value of a StringVar from a widget in one page (PageOne) in another page (PageTwo).

Solution: Leveraging your Controller

Utilizing the controller, you can establish communication between pages. Firstly, save a reference to the controller within each page:

<code class="python">class PageOne(ttk.Frame):
    def __init__(self, parent, controller):
        self.controller = controller
        ...

class PageTwo(ttk.Frame):
    def __init__(self, parent, controller):
        self.controller = controller
        ...</code>

Secondly, incorporate a method in the controller that retrieves a page based on its class name:

<code class="python">class MyApp(Tk):
    ...
    def get_page(self, classname):
        '''Returns an instance of a page given it's class name as a string'''
        for page in self.frames.values():
            if str(page.__class__.__name__) == classname:
                return page
        return None</code>

With this method, pages can access each other by calling this function and gaining a reference to the target page. Subsequently, you can access the shared members of that page, like so:

<code class="python">class PageTwo(ttk.Frame):
    ...
    def print_it(self):
        page_one = self.controller.get_page("PageOne")
        value = page_one.some_entry.get()
        print ('The value stored in StartPage some_entry = %s' % value)</code>

Alternative Solution: Storing Data in the Controller

To avoid tight coupling between pages, consider storing shared data in the controller. This method allows pages to be independent of each other's internal designs:

<code class="python">class MyApp(Tk):
    def __init__(self):
        ...
        self.app_data = {"name":    StringVar(),
                         "address": StringVar(),
                         ...
                        }</code>

Modify pages to reference the controller when creating widgets:

<code class="python">class PageOne(ttk.Frame):
    def __init__(self, parent, controller):
        self.controller=controller
        ...
        self.some_entry = ttk.Entry(self,
            textvariable=self.controller.app_data["name"], ...) </code>

Finally, access data from the controller, eliminating the need for get_page:

<code class="python">    def print_it(self):
        value = self.controller.app_data["address"].get()
        ...</code>

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