Author: John Au-Yeung

Web developer specializing in React, Vue, and front end development.

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Python Answers

How to fix ProgrammingError: SQLite objects created in a thread can only be used in that same thread with Python SQLite3?

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Sometimes, we want to fix ProgrammingError: SQLite objects created in a thread can only be used in that same thread with Python SQLite3

In this article, we’ll look at how to fix ProgrammingError: SQLite objects created in a thread can only be used in that same thread with Python SQLite3.

How to fix ProgrammingError: SQLite objects created in a thread can only be used in that same thread with Python SQLite3?

To fix ProgrammingError: SQLite objects created in a thread can only be used in that same thread with Python SQLite3, we can call sqlite3.connect with check_same_thread set to False.

For instance, we wrikte

conn = sqlite3.connect('your.db', check_same_thread=False)

to call sqlite3.connect with the check_same_thread set to False so that SQLite objects created in any thread can be used in any other thread.

Conclusion

To fix ProgrammingError: SQLite objects created in a thread can only be used in that same thread with Python SQLite3, we can call sqlite3.connect with check_same_thread set to False.

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Python Answers

How to fix Python Flask Value error view function did not return a response?

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Sometimes, we want to fix Python Flask Value error view function did not return a response.

In this article, we’ll look at how to fix Python Flask Value error view function did not return a response.

How to fix Python Flask Value error view function did not return a response?

To fix Python Flask Value error view function did not return a response, we should return a response in our view.

For instance, we write

@app.route('/')
def my_form():
    return render_template("my-form.html")

to call render_template with the template file name to return the template with the given file name as the response.

Conclusion

To fix Python Flask Value error view function did not return a response, we should return a response in our view.

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Python Answers

How to include a HTML file in a Jinja2 template with Python Flask?

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Sometimes, we want to include a HTML file in a Jinja2 template with Python Flask.

In this article, we’ll look at how to include a HTML file in a Jinja2 template with Python Flask.

How to include a HTML file in a Jinja2 template with Python Flask?

To include a HTML file in a Jinja2 template with Python Flask, we can use the include directive.

For instance, we write

{% extends 'template.html' %}
{% block content %}
    {% if task == 'content1' %}
        {% include 'content1.html' %}
    {% endif %}
    {% if task == 'content2' %}
        {% include 'content2.html' %}
    {% endif %}
{% endblock %}

to render content1.html and content2.html‘s contents with

{% include 'content1.html' %}

and

{% include 'content2.html' %}

Conclusion

To include a HTML file in a Jinja2 template with Python Flask, we can use the include directive.

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Python Answers

How to download a csv file on clicking a button with Python Flask?

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Sometimes, we want to download a csv file on clicking a button with Python Flask.

in this article, we’ll look at how to download a csv file on clicking a button with Python Flask.

How to download a csv file on clicking a button with Python Flask?

To download a csv file on clicking a button with Python Flask, we can add a link that goes to the view that returns the csv as the response.

For instance, we write

from flask import Flask, Response
app = Flask(__name__)

@app.route("/")
def hello():
    return '''
        <html>
          <body>
            <a href="/get_csv">Click me.</a>
          </body>
        </html>
      '''

@app.route("/get_csv")
def get_csv():
    csv = '1,2,3\n4,5,6\n'
    return Response(
        csv,
        mimetype="text/csv",
        headers={"Content-disposition":
                 "attachment; filename=myplot.csv"})


app.run(debug=True)

to create the hello route that renders the HTML with the link.

Then add the get_csv view that returns the csv as the response by creating a Response object with mimetype set to 'text/csv' and the csv as the content.

Now when we click on the link, the csv should be downloaded as myplot.csv.

Conclusion

To download a csv file on clicking a button with Python Flask, we can add a link that goes to the view that returns the csv as the response.

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Python Answers

How to make a Python asyncio call from a Flask route?

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Sometimes, we want to make a Python asyncio call from a Flask route.

In this article, we’ll look at how to make a Python asyncio call from a Flask route.

How to make a Python asyncio call from a Flask route?

To make a Python asyncio call from a Flask route, we can call run_until_complete.

For instance, we write

import asyncio
from flask import Flask

async def foo(a):
    print(a)

loop = asyncio.get_event_loop()
app = Flask(__name__)

@app.route("/")
def notify():
    loop.run_until_complete(foo("abc"))
    return "OK"

if __name__ == "__main__":
    app.run(debug=False, use_reloader=False)

to create the event loop with get_event_loop.

Then we call loop.run_until_complete with the async function to run in the notify view.

Conclusion

To make a Python asyncio call from a Flask route, we can call run_until_complete.