[BUG] Flask 2.2.0 unbound_message error.

Explanation of the problem

The context environment is running in Docker with three Dockerfiles, namely ubuntu:latest, python:latest, and dash:latest. The ubuntu:latest dockerfile starts with the Ubuntu 20.04 base image, sets the environmental variables, updates and upgrades the packages, installs ca-certificates, tzdata, and locales, and removes the timezone and localtime files. Then, it sets the timezone to Europe/Berlin, generates the locale, and sets the default locale to en_US.UTF-8.

The python:latest dockerfile starts with the ubuntu:latest image, sets the environmental variables, installs build-essential, zlib1g-dev, libncurses5-dev, libgdbm-dev, libnss3-dev, libssl-dev, libreadline-dev, libffi-dev, libsqlite3-dev, wget, libbz2-dev, and curl, creates a temp directory, downloads and extracts Python 3.10.2, configures and installs it, removes the temp directory, and installs the requests library.

The dash:latest dockerfile starts with the python:latest image, installs the dash, dash-renderer, dash-html-components, dash-core-components, plotly, gunicorn, and Flask libraries, exposes the port 5000, copies the .py files to the app directory, and starts the app with gunicorn.

The docker file starts with the dash:latest image, exposes the port 5000, copies the requirements.txt file to the temp directory, installs the libraries in the requirements.txt file, removes the requirements.txt file, copies the current directory to the app directory, and starts the app with gunicorn.

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Problem solution for: [BUG] Flask 2.2.0 unbound_message error.

Based on the top answers, it seems like there is an issue with Flask 2.2.0 that is causing an error message indicating “got an unexpected keyword argument ‘unbound_message'”. The error message is likely related to a function or method call that includes the ‘unbound_message’ argument. Pinning an earlier version of Flask may fix the issue for the time being.

The error message “got an unexpected keyword argument ‘unbound_message'” is a common issue that users encounter when trying to use Flask with certain dependencies. The root of the problem lies in the fact that the Flask 2.2.0 version introduced changes to the way unbound messages are handled. Specifically, a new parameter called “unbound_message” was added to the flash() method to allow users to specify a custom message for unbound errors. This change is not backward compatible with some dependencies, leading to the error message.

The proposed solution to this issue is to pin an earlier version of Flask. This involves specifying the version number of Flask that does not have the breaking changes introduced in version 2.2.0. For example, you can pin Flask to version 2.1.0 by including the following line in your requirements.txt file:

Flask==2.1.0

It is worth noting that the issue may not be limited to Flask itself, but may be caused by certain dependencies that rely on Flask. In this case, pinning Flask to an earlier version may not solve the problem. Therefore, it is important to investigate the specific dependencies that are causing the issue and determine whether they are compatible with Flask 2.2.0. If not, you may need to use alternative dependencies or find a workaround that does not rely on the incompatible dependencies.

Other popular problems with Dash

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Input(id='input', value='', type='text'),
    html.Div(id='output')
])

@app.callback(Output('output', 'children'),
              [Input('input', 'value')])
def update_output(value):
    return value.upper()

if __name__ == '__main__':
    app.run_server(debug=True)

import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Input(id='input', value='', type='text'),
    html.Div(id='output')
])

@app.callback(Output('output', 'children'),
              [Input('input', 'value')])
def update_output(value):
    return value.upper()

if __name__ == '__main__':
    app.run_server(debug=True)

import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Input(id='input', value='', type='text'),
    html.Div(id='output')
])

@app.callback(Output('output', 'children'),
              [Input('input', 'value')])
def update_output(value):
    return value.upper()

if __name__ == '__main__':
    app.run_server(debug=True)

A brief introduction to Dash

Most popular use cases for Dash

import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly.express as px
import pandas as pd

# Load sample data
df = pd.read_csv('data.csv')

# Create scatter plot
fig = px.scatter(df, x='x_axis_column', y='y_axis_column')

# Define the Dash app layout
app = dash.Dash(__name__)
app.layout = html.Div(children=[
    dcc.Graph(figure=fig)
])

# Run the Dash app
if __name__ == '__main__':
    app.run_server(debug=True)

import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly.express as px
import pandas as pd

# Load sample data
df = pd.read_csv('data.csv')

# Define the Dash app layout
app = dash.Dash(__name__)
app.layout = html.Div(children=[
    dcc.Dropdown(
        options=[{'label': country, 'value': country} for country in df['country'].unique()],
        value='United States'
    ),
    dcc.Graph(id='population-graph')
])

# Define the Dash app callbacks
@app.callback(
    dash.dependencies.Output('population-graph', 'figure'),
    [dash.dependencies.Input('country-dropdown', 'value')]
)
def update_population_graph(country):
    country_df = df[df['country'] == country]
    fig = px.line(country_df, x='year', y='population')
    return fig

# Run the Dash app
if __name__ == '__main__':
    app.run_server(debug=True)