Multi Page Apps: circular reference when importing app

I define my dash app instance in app.py:

server = flask.Flask(__name__)
app = Dash(__name__,
        plugins=[dl.plugins.pages],
        external_stylesheets=external_stylesheets,
        external_scripts=external_scripts, server=server)

By default the pages plug-in iterates over the modules in the ./pages folder. I have a page that needs to reference the dash app instance in order to call the get_asset_url() method.

In my page module, the import:

from app import app

Creates a circular reference. I can fix this with an embedded import but I’d prefer not to. Is there a way to resolve this? Ideally a proxy reference to the current dash instance (dash.current_app) would be one solution.

Cheers.

[AnnMarieW]

@stevej2608, @M4thM4gician To solve the circular reference issue we will be adding the following functions that will be similar to dash.callback where the appobject is not needed. This is on the project plan to be completed before pages/ is moved into Dash.

• dash.get_relative_path
• dash.strip_relative_path
• dash.get_asset_url

This is a good first issue. Here are some tips for getting started:

• The pull request will be in dash, rather than here in dash-labs
• The solution will be similar to how dash.callback was created. Here is the pull request

Related issues:

• dash.long_callback

• as raised on the forum in the post from @ bigmike

Are there plans to integrate a solution to accessing the cache in callbacks outside the app.py file? For example, I have multipage app that uses a structure similar to the “Caching and Signaling” example in the docs. Once the expensive query is complete, callbacks on every page will be utilizing this same data source and need to access the global cache. Since the cache is tied to the app object, I haven’t been able to make this work on a multipage setup without just putting all my callbacks inside the app.py file. This quickly becomes hard to navigate with a larger multipage app.

[bigmike36c]

Just to add to this, the same issue occurs with the dashboard engine for enterprise users. The workaround is easy enough by simply registering the dashboard engine page and declaring its layout inside the app.py file. However, for code organization, it would be nice to eventually be able to break this code and the associated callbacks into its own file.