[javascript] Flask - Calling python function on button OnClick event

I am new to python and Flask. I have a Flask Web App with a button. When I click on the button I would like to execute a python method not a Javascript method. How can I do this?

I have seen examples with python where it redirects me to a new page using a form tag like this

<form action="/newPage" method="post">

but I don't want it to redirect me to a new page. I just want it to execute the python method. I am making this for a Raspberry Pi robot car. When I press the forward button, I want it to run the method to Turn wheels forward.

Button HTML Code (index.html)

<button name="forwardBtn" onclick="move_forward()">Forward</button>

simple app.py Code - move_forward() method located here

#### App.py code

from flask import Flask, render_template, Response, request, redirect, url_for
app = Flask(__name__)

def index():
    return render_template('index.html');

def move_forward():
    #Moving forward code
    print("Moving Forward...")

I have seen similar questions to mine on Stackoverflow, but they don't seem to answer my question or I am unable to understand the answer. If someone could please provide me a simple way to call a Python method on button click event, it would be greatly appreciated.

Other Questions that I have looked at:

--Python Flask calling functions using buttons

--Calling a python function with a button

--Flask Button run Python without refreshing page?

This question is related to javascript python html flask raspberry-pi

The answer is

It sounds like you want to use this web application as a remote control for your robot, and a core issue is that you won't want a page reload every time you perform an action, in which case, the last link you posted answers your problem.

I think you may be misunderstanding a few things about Flask. For one, you can't nest multiple functions in a single route. You're not making a set of functions available for a particular route, you're defining the one specific thing the server will do when that route is called.

With that in mind, you would be able to solve your problem with a page reload by changing your app.py to look more like this:

from flask import Flask, render_template, Response, request, redirect, url_for
app = Flask(__name__)

def index():
    return render_template('index.html')

@app.route("/forward/", methods=['POST'])
def move_forward():
    #Moving forward code
    forward_message = "Moving Forward..."
    return render_template('index.html', forward_message=forward_message);

Then in your html, use this:

<form action="/forward/" method="post">
    <button name="forwardBtn" type="submit">Forward</button>

...To execute your moving forward code. And include this:

{{ forward_message }} 

... where you want the moving forward message to appear on your template.

This will cause your page to reload, which is inevitable without using AJAX and Javascript.

Easiest solution

<button type="button" onclick="window.location.href='{{ url_for( 'move_forward') }}';">Forward</button>

index.html (index.html should be in templates folder)

<!doctype html>

    <title>The jQuery Example</title>

    <h2>jQuery-AJAX in FLASK. Execute function on button click</h2>  

    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"> </script>
    <script type=text/javascript> $(function() { $("#mybutton").click(function (event) { $.getJSON('/SomeFunction', { },
    function(data) { }); return false; }); }); </script> 

        <input type = "button" id = "mybutton" value = "Click Here" />



from flask import Flask, jsonify, render_template, request
app = Flask(__name__)

def index():
    return render_template('index.html')

def SomeFunction():
    print('In SomeFunction')
    return "Nothing"

if __name__ == '__main__':

You can simply do this with help of AJAX... Here is a example which calls a python function which prints hello without redirecting or refreshing the page.

In app.py put below code segment.

#rendering the HTML page which has the button
def json():
    return render_template('json.html')

#background process happening without any refreshing
def background_process_test():
    print ("Hello")
    return ("nothing")

And your json.html page should look like below.

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type=text/javascript>
        $(function() {
          $('a#test').on('click', function(e) {
                function(data) {
              //do nothing
            return false;

<div class='container'>
            <a href=# id=test><button class='btn btn-default'>Test</button></a>


Here when you press the button Test simple in the console you can see "Hello" is displaying without any refreshing.

Examples related to javascript

need to add a class to an element How to make a variable accessible outside a function? Hide Signs that Meteor.js was Used How to create a showdown.js markdown extension Please help me convert this script to a simple image slider Highlight Anchor Links when user manually scrolls? Summing radio input values How to execute an action before close metro app WinJS javascript, for loop defines a dynamic variable name Getting all files in directory with ajax

Examples related to python

programming a servo thru a barometer Is there a way to view two blocks of code from the same file simultaneously in Sublime Text? python variable NameError Why my regexp for hyphenated words doesn't work? Comparing a variable with a string python not working when redirecting from bash script is it possible to add colors to python output? Get Public URL for File - Google Cloud Storage - App Engine (Python) Real time face detection OpenCV, Python xlrd.biffh.XLRDError: Excel xlsx file; not supported Could not load dynamic library 'cudart64_101.dll' on tensorflow CPU-only installation

Examples related to html

Embed ruby within URL : Middleman Blog Please help me convert this script to a simple image slider Generating a list of pages (not posts) without the index file Why there is this "clear" class before footer? Is it possible to change the content HTML5 alert messages? Getting all files in directory with ajax DevTools failed to load SourceMap: Could not load content for chrome-extension How to set width of mat-table column in angular? How to open a link in new tab using angular? ERROR Error: Uncaught (in promise), Cannot match any routes. URL Segment

Examples related to flask

Flask at first run: Do not use the development server in a production environment Flask - Calling python function on button OnClick event python-How to set global variables in Flask? In Flask, What is request.args and how is it used? How to print from Flask @app.route to python console What does "app.run(host='') " mean in Flask Making an asynchronous task in Flask Flask ImportError: No Module Named Flask can you add HTTPS functionality to a python flask web server? How to get http headers in flask?

Examples related to raspberry-pi

Flask - Calling python function on button OnClick event How to Update Date and Time of Raspberry Pi With out Internet How do I use setsockopt(SO_REUSEADDR)? How to change screen resolution of Raspberry Pi Default settings Raspberry Pi /etc/network/interfaces Cannot find module cv2 when using OpenCV How to install the Raspberry Pi cross compiler on my Linux host machine? Hook up Raspberry Pi via Ethernet to laptop without router? Python AttributeError: 'module' object has no attribute 'Serial'