03-flask-intro.md

5.3 Web services: introduction to Flask

Slides

Links

• 0.0.0.0 vs localhost
• Top-level script enviroment
• route decorator

Notes

In this session we talked about what is a web service and how to create a simple web service.

• What is actually a web service
  • A web service is a method used to communicate between electronic devices.
  • There are some methods in web services we can use it to satisfy our problems. Here below we would list some.
    • GET: GET is a method used to retrieve files, For example when we are searching for a cat image in google we are actually requesting cat images with GET method.
    • POST: POST is the second common method used in web services. For example in a sign up process, when we are submiting our name, username, passwords, etc we are posting our data to a server that is using the web service. (Note that there is no specification where the data goes)
    • PUT: PUT is same as POST but we are specifying where the data is going to.
    • DELETE: DELETE is a method that is used to request to delete some data from the server.
    • For more information just google the HTTP methods, You'll find useful information about this.
• To create a simple web service, there are plenty libraries available in every language. Here we would like to introduce Flask library in python.
  • If you haven't installed the library just try installing it with the code pip install Flask
  • To create a simple web service just run the code below:

  • from flask import Flask
    
    app = Flask('ping') # give an identity to your web service
    
    @app.route('/ping', methods=['GET']) # use decorator to add Flask's functionality to our function
    def ping():
        return 'PONG'
    
    if __name__ == '__main__':
       app.run(debug=True, host='0.0.0.0', port=9696) # run the code in local machine with the debugging mode true and port 9696

  • With the code above we made a simple web server and created a route named ping that would send pong string.
  • To test it just open your browser and search localhost:9696/ping, You'll see that the 'PONG' string is received. Congrats You've made a simple web server 🥳.
• To use our web server to predict new values we must modify it. See how in the next session.

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• Notes from Peter Ernicke

Navigation

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