Ajax python flask

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Ajax python flask

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ajax python flask

Some objects are easy to serialise and de-serialise with off the shelf functions. See an example based your code modified below Ignore the CORS as that's due to my test evironment set up. You're not passing it an object, you're passing it a string, which is then converted into JSON again. Because the request data contains double-encoded JSON, the request. Learn more. Flask request. Asked 1 year, 4 months ago. Active 2 days ago. Viewed 5k times. Baki Baki 2 2 silver badges 8 8 bronze badges.

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Question Close Updates: Phase 1. Visit chat. Related Hot Network Questions. Question feed. Stack Overflow works best with JavaScript enabled.This is the fourteenth installment of the Flask Mega-Tutorial series, in which I'm going to add a live language translation feature, using the Microsoft translation service and a little bit of JavaScript.

Note 1: If you are looking for the legacy version of this tutorial, it's here. Note 2: If you would like to support my work on this blog, or just don't have patience to wait for weekly articles, I am offering the complete version of this tutorial packaged as an ebook or a set of videos. For more information, visit courses. In this article I'm going to take a departure from the "safe zone" of server-side development and to work on a feature that has equally important server and client-side components.

Have you seen the "Translate" links that some sites show next to user generated content?

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These are links that trigger a real time automated translation of content that is not in the user's native language. The translated content is typically inserted below the original version.

ajax python flask

Google shows it for search results in foreign languages. Facebook does it for posts. Twitter does it for tweets. Today I'm going to show you how to add the very same feature to Microblog!

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In the traditional server-side model that I've followed so far there is a client a web browser commanded by a user making HTTP requests to the application server.

A request can simply ask for an HTML page, like when you click the "Profile" link, or it can trigger an action, like when you click the Submit button after editing your profile information. In both types of requests the server completes the request by sending a new web page to the client, either directly or by issuing a redirect.

The client then replaces the current page with the new one. This cycle repeats for as long as the user stays on the application's web site. In this model the server does all the work, while the client just displays the web pages and accepts user input.

There is a different model in which the client takes a more active role. In this model, the client issues a request to the server and the server responds with a web page, but unlike the previous case, not all the page data is HTML, there is also sections of the page with code, typically written in Javascript.

Once the client receives the page it displays the HTML portions, and executes the code. From then on you have an active client that can do work on its own without little or no contact with the server.

ajax python flask

In a strict client-side application the entire application is downloaded to the client with the initial page request, and then the application runs entirely on the client, only contacting the server to retrieve or store data and making dynamic changes to the appearance of that first and only web page. Most applications are a hybrid between the two models and combine techniques of both. My Microblog application is mostly a server-side application, but today I will be adding a little bit of client-side action to it.

To do real time translations of user posts, the client browser will send asynchronous requests to the server, to which the server will respond without causing a page refresh. The client will then insert the translations into the current page dynamically. The application has good support for foreign languages thanks to Flask-Babel, which would make it possible to support as many languages as I can find translators for.

But of course, there is one element missing. Users are going to write blog posts in their own languages, so it is quite possible that a user will come across posts that are written in unknown languages. The quality of automated translations isn't always great, but in most cases it is good enough if all you want is to have a basic idea of what a text in another language means.

This is an ideal feature to implement as an Ajax service. Consider that the index or explore pages could be showing several posts, some of which might be in foreign languages.

MicroPython and the Internet of Things

If I implement the translation using traditional server-side techniques, a request for a translation would cause the original page to get replaced with a new page. The fact is that requesting a translation for one out of many displayed blogs posts isn't a big enough action to require a full page update, this feature works much better if the translated text is dynamically inserted below the original text while leaving the rest of the page untouched.I have already covered an introductory article on getting started with python web application development using Python Flask and MySQL.

Prior to getting started with this tutorial, make sure you have Python installed. Setting up Flask using pip is quite easy. Create a app directory called FlaskAppnavigate to it and create app. First we imported the Flask module and then created a flask app instance. Your app must be now running.

Here is how signUp. Next add a method called signUp on the python side to handle the request and render the corresponding html file.

Here is how it looks like. Create a new JavaScript file called script. Here is how the script. Now add a python method called signUpUser to receive the data from client side. Here is how it looks like:. We have explicitly defined the method that it supports using the methods attribute. In order to retrieve the posted parameters we have made use of the request module. We have also used json module to return json data to the client side. Check browser console to see the returned json data.

Do let us know your thoughts, suggestions or corrections in the comments below. The code from the above tutorial is available in GitHub.

I blog about web development related tutorials and articles in my free time.I'm a software developer and IT consultant. Want to hire me for a project? See my company's service offering. During the weekend, I discovered Bokeha Python visualization library for the web. The samples looked nice, so I played around a bit, mostly following the accessible Quick Start guide. Eventually, I decided to build a small dashboard with Bokeh for an existing Flask application and wanted the plots to automatically fetch data updates using AJAX requests.

ajax python flask

This meant fiddling around a bit and reading more documentation. If you plan on doing something similar, the following write-up hopefully saves you some time and pitfalls.

With Bokeh you can build stand-alone and server-based data visualizations. The stand-alone visualizations are generated once in your Python environment and then saved to a file or just delivered to a browser. The plots are then drawn and made interactive using BokehJS, the client-side JavaScript library, that needs to be included in your page.

If you want your visualizations to be based on large datasets, use streaming data, auto-downsamling for efficiency, and other goodness, you can use the Bokeh Server component. To simulate our exisiting application, we quickly install Flask into a virtual environment, and create a simple app.

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I wrote a short guide on how to do this on macOS. To set things up, we first create two template files for our page skeleton. Add a layout. In a nutshell: we have our base html skeleton layout.

In dashboard. Time to start plotting: in app. We imported figure and components from Bokeh. To keep things simple, we just gave the Figure object a height and a responsive width. To create a line chart or, in Bokeh terms: to add line glyphswe then used the line method, passing in our prepared lists of x and y. There are various ways to style the plot further, control what widgets are shown, etc.

For refreshing our plot via an AJAX request we have two options: either we replace the whole data for the plot with the data returned by our web app, or we only deliver data updates and then append this data to the plot.

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To keep track of where we are, we simply keep the state of x in a global variable. Depending on what you are doing, you may also want to keep track of different states and not just one global state until the app is restarted. If your dataset is not too large, you might as well be fine with the replace option. In app. We need jsonify and request from Flask to format our data output and get our url. And we need AjaxDataSource from Bokeh, to tell the plot that we have a http data source.

We additionally set the update interval to 2 seconds, and choose the append mode the other option would be replacesee above. Note that we are not regenerating the whole components for every update.If you are new to web development, have a strong python background, AND have a desire to take you technical skills to the next level, this article is for you. I will take you through the journey of full stack development with python from conceptualizing an idea to a fully deployed dynamic web application.

Full Stack Web Development — Python/flask/javascript/jQuery/bootstrap

The proof of concept dynamic web application we built that I will be referring to is stockbacktest. Flask is a python microframework that has the principle of having as little tech as possible to get a website up and running. Create a file called application. Run the web app using this command:. As you add more and more to your web application your file structure will start to look like the following:. This is the routing file — All pages of your website will be directed from here. All of your html files that you serve based on your routing in the application.

All of your static files live here and can have any number of sub folders — All of your css, js, icons, images, etc files. To reference these files to your working html you need to path them. Below is an example of reference to a css style to a given html template:.

All of your back-end custom code — You can structure this as more folders within your working project directory or sub folders. This follows normal python principles of importing code to other python files. The virtual environment that isolates your python package dependencies not necessary, but makes your life a lot easier at time of deployment.

To run your web application:. To deactivate virtual environment and return to working directory of your project:. We started this journey with the goal of deploying a web application that people could interact with and use for free.

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Given our interest in the financial sector and familiarity of Quandlwe decided to build a stock backtesting web application where the user can play around with a few inputs and see what the backtest resulted in. Below is a chronological outline of what I will be highlighting in the next 6 sections that took place during development of stockbacktest. This is roughly the order of operations that took place — There was a lot of back and forth between the back-end with the form submitting and the dashboard layout.

As you can imagine, there can be a lot of work tying together back-end code with front-end variable objects. With the objective of building a web application where the user could change around a few inputs and see what a given model resulted in, I needed to make classes so I could instantiated objects of each class.

Below is part of the MeanReversion class illustrating this on the back-end:. Within the routing application. Below is the python code that powers the validation of the form of the correlation page :.

Then, within the routing the application.

Flask and AJAX

Next, within the served correlation. If it does not, the routing returns the correlation. By having form validators as your first line of defense for creating a better user experience, it can help save a ton of custom code that you would have to write otherwise.

Furthermore, it creates quicker user feedback no back-end code runs until the validation is completed. Bootstrap provides a ton out of the box to make your life easier on the front-end to make things look nice. For example, we used code in the gist below to make the scorecard features the high level cards on the top of the dashboards layout differently based upon wether you are viewing on desktop or mobile:.

The above html code will give the following layouts depending on desktop viewing or mobile viewing iphone 6 in this case :. Going into this project, the biggest deficiency I had was anything related to front-end interaction by the user.

For all the forms of the backtests, we wanted to create a user experience where the available dates you can select correspond to the actual available data from Quandl. Not only does this create a better user experience for the user on the front end, but can also tremendously save the response time of the results not pulling more data than you need from Quandl on the back-end.It is very easy for the humans to read and write JSON.

Calling it is very easy.

Using jQuery to Update a Page Without Refresh (Part 1 of 2)

The user will enter the first name and last name and the data will be sent to the flask route as Post request and it will display the value of the field in the HTML. The following is the HTML code. If you want to know more about Bootstrap. You can read the documentation on the bootstrap. We have made two input fields to be entered by the user. After entering the input field you will call the Ajax Javascript part that will finally display the combination of the values that is First Name and Last Name.

It will display just after the submit button. Ajax is a framework of the Javascript. Ajax requires the following class and ids of the above HTML code for performing the functions. Now after reading the Ajax code you will learn how the ajax functions communicate with these class and ids to perform the tasks. First of keeping it in mind that to run the entire Ajax part without any errors you have to include the main jquery part. You can add jquery from the Google hosted libraries. At the writing, this post jquery version was 3.

The complete code will gives the output without reloading the page. It will prevent the Jquery for doing the default action of the element for performing tasks. In the function, I have done the ajax part. It will be like the following. After that URL value. The statement.

You can think it will be the main output when the submit button is clicked. For the beginners, It is difficult for the above Ajax part to remember. The following steps you should keep in mind. In the next section, You will learn how to do the URL part. We will use the Python web framework Flask. There will be posting the data and showing the output in the HTML attributes.Something a lot of beginners struggle with is the concept of passing data between different programming languages.

Serializing data means taking a value, object, or data structure, and translating it into a format that can be stored or transmitted. Most importantly, it needs to be put back together at the other end. JSON is a human-readable format and is straightforward for machines to read and write. The specification is small enough to read during one cup of coffee. JSON is built on two data structures. This works in the browser as well as Node.

In Python, first import the json module then serialize with json. It requires two OS-specific commands to install and run a debug server.

Code along or fork this repository to grab the code for all the examples. Everything happens in the console. When you POST mail, you head to the post office with your letter filled with information. However, do note that you should be adding catch to the end of these Promises.

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Docs for catch here. A temperature sensor. We want to listen to that program and store the values it reports. More information on Python flushing here. We also make sure that the end of the printed statement contains no extra information even though parseFloat would clean it! Piping the data between the two running languages. A Node. You can run node temperature-listener. The array of temperatures will grow as new data arrives, and our debug log line will result in the following output.

There are many ways to pass data between these two languages.


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