Dash Uploader callbacks fail in a Multi-page app with Dash Extensions
yordanovn opened this issue · 1 comments
Hi,
I'm building a multi-page Dash application. It utilises functionality from the dash-extensions
package, however I experience issues when I want to use a dash-uploader
callback function.
The error I get is: AttributeError: 'DashProxy' object has no attribute 'blueprint'.
I managed to figure out that it occurs, because the DashProxy's callback
method is using the blueprint
attribute, however the du.callback
is trying to call it before the attribute is assigned to the instance. I don't know how to work around this issue.
Note: I'm not sure if dash-uploader
is supposed to work with dash-extensions
and this is an issue or rather a feature request.
Here's how the code is structured:
app.py:
from dash_extensions.enrich import DashProxy, ServersideOutputTransform
app = DashProxy(__name__, use_pages=True, transforms=[ServersideOutputTransform()])
file_upload.py:
import dash
from dash import html, Output
import dash_uploader as du
app = dash.get_app()
du.configure_upload(app=app, folder='./uploads')
dash.register_page(__name__, path='/')
layout = html.Div(children=[
du_file_upload := du.Upload(id='du-file-upload'),
du_uploads := html.Div(id='du-uploads')
] )
@du.callback(
output=Output("du-uploads", "children"),
id="du-file-upload",
)
def get_a_list(filenames):
return html.Ul([html.Li(filenames)])
Here is the full Traceback:
Traceback (most recent call last):
File "/Users/user/PycharmProjects/machine-learning/ROICalculator/ticket_analysis/app.py", line 16, in <module>
app = DashProxy(__name__, use_pages=True, transforms=[ServersideOutputTransform()])
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash_extensions/enrich.py", line 352, in __init__
super().__init__(*args, **kwargs)
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash/dash.py", line 494, in __init__
self.init_app()
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash/dash.py", line 578, in init_app
self.enable_pages()
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash/dash.py", line 2044, in enable_pages
self._import_layouts_from_pages()
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash/dash.py", line 2016, in _import_layouts_from_pages
spec.loader.exec_module(page_module)
File "<frozen importlib._bootstrap_external>", line 843, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "/Users/user/PycharmProjects/machine-learning/ROICalculator/ticket_analysis/pages/file_upload.py", line 101, in <module>
def get_a_list(filenames):
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash_uploader/callbacks.py", line 105, in add_callback
dash_callback = settings.app.callback(
File "/Users/user/virtualenv/ticket-analysis/lib/python3.8/site-packages/dash_extensions/enrich.py", line 358, in callback
return self.blueprint.callback(*args, **kwargs)
AttributeError: 'DashProxy' object has no attribute 'blueprint'
I managed to resolve my issue by unwrapping the du.callback
method within my own page definition.
The change is that instead of calling app.callback
which would have used DashProxy.callback
we now call callback
which is imported from dash
. By doing this we are bypassing the issue that the blueprint
attribute doesn't yet exist for the DashProxy
instance.
I will keep the issue as Open, since there still might be a fix or a documentation update within the dash-uploader
project to better accommodate integration with dash-extensions
.
Here is an example:
app.py:
from dash_extensions.enrich import DashProxy, ServersideOutputTransform
app = DashProxy(__name__, use_pages=True, transforms=[ServersideOutputTransform()])
file_upload.py:
import dash
from dash import html, Output
import dash_uploader as du
from dash_uploader.callbacks import create_dash_callback
import dash_uploader.settings as settings
app = dash.get_app()
du.configure_upload(app=app, folder='./uploads')
dash.register_page(__name__, path='/')
layout = html.Div(children=[
du_file_upload := du.Upload(id='du-file-upload'),
du_uploads := html.Div(id='du-uploads')
] )
def update_du_uploads(filenames):
return html.Ul([html.Li(filenames)])
dash_callback = create_dash_callback(
update_du_uploads,
settings,
)
callback(
Output('du-uploads', 'children'),
Input('du-file-upload', 'isCompleted'),
State('du-file-upload', 'fileNames'),
State('du-file-upload', 'upload_id')
)(dash_callback)