Table of Contents
What is Flask?
In simple words, Flask is one of the popular frameworks of Python, similar to the Django framework. However, before we get deep into this topic, let’s look into what web frameworks are.
While writing complex code, programmers do not have enough time to write low-level codes continually. So they use valuable features such as frameworks that deal with low-level concepts such as thread management, protocols, etc. Flask is one such framework.
Flask is built on the Werkzeug WSGI toolkit and Jinja2 template engine, both of which are Pocoo products.
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How to use Flask
To use Flask, one needs to install it. Flask is compatible with Python 2.6 or the higher versions.
Installing Python Flask
To install it, you must first create an isolated environment for it, and this is achieved with the help of a virtual Python environment builder called virtualenv.
virtualenvhelps users create multiple environments side by side and allows you to work on numerous projects simultaneously on the same machine.
To install virtualenv on windows:
pip install virtualenv
After installing, the environment is activated using the following:
venv\scripts\activate
To install virtualenv on Linux:
Sudo apt-get install virtualenv
After installing the environment is created in,
mkdir newproj
cd newproj
virtualenv venv
After installing, the environment is activated on Linux using the following:
venv/bin/activate
After the above steps, finally, Flask is installed in Python using,
pip install Flask
To test whether Flask is installed in the editor:
from flask import Flask
app = Flask(__name__) # Flask constructor
@app.route('/')
def hello_world():
return 'Hello World’
if __name__ == '__main__':
app.run()
In the above code,
- The current module’s name
(__name__)is passed as an input to the Flask function Object().
- The Flask class’s route() function is a decorator that instructs the application which URL should be used to call the related function.
app.route(rule, options)
- The rule parameter represents the function’s URL binding.
- The parameters to be passed to the underlying rule object are listed in the options.
- Since in this code, the URL ‘/’ is bound with the function
hello_world(), the output of this function will be released when the homepage of the webserver is opened in the browser.
What is Flask Used For?
It offers a plethora of features to developers looking forward to building complex web or mobile applications. With the help of Flask, you can build blogging platforms, content sites, and many more complex applications.
To start the flask application, we use the run() function:
app.run()
The above code is used to start the function, but while working on a code and making changes, the server must be reloaded on its own. But, the server does not reload on its own but manually. To avoid such minor inconvenience, we use the debug property.
Using the debug property, the server reloads on its own at every code change and will also help in tracking errors.
The debug property is added as follows:
app.debug = True
app.run()
app.run(debug = True)
Routing:
Another primary reason to use Flask is for its routing property.
For the users to not confuse with the URLs, web frameworks provide routing techniques helping the user remember the URLs.
Navigating directly to a web page without leaving the Home page by using routing is possible.
This is achieved by the route() decorator that binds the URL to a function:
@app.route('/hello')
def hello_world():
return 'hello world'
The hello-world() function is connected to the URL ‘/hello’ rule. As a result, when a visitor hits http://localhost:5000/hello, the browser will display the output of the hello world() function.
Why Use Flask?
You may use it to construct complicated and straightforward web applications and applications that are integrated with machine learning algorithms. Developers can make use of their lightweight framework to:
- Integrated support for unit testing
- Support for secure cookies
- Create APIs easily
- Supports Visual Debugging
- Can be integrated efficiently with all the major databases integrate easily with complex databases
- Use Ninja Templating Engine
Also, it is easier to grasp compared to other frameworks.
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What is Flask Python
What is a Web Framework?
A Web Application Framework or a simply a Web Framework represents a collection of libraries and modules that enable web application developers to write applications without worrying about low-level details such as protocol, thread management, and so on.
What is Flask?
Flask is a web application framework written in Python. It was developed by Armin Ronacher, who led a team of international Python enthusiasts called Poocco. Flask is based on the Werkzeg WSGI toolkit and the Jinja2 template engine.Both are Pocco projects.
WSGI
The Web Server Gateway Interface (Web Server Gateway Interface, WSGI) has been used as a standard for Python web application development. WSGI is the specification of a common interface between web servers and web applications.
Werkzeug
Werkzeug is a WSGI toolkit that implements requests, response objects, and utility functions. This enables a web frame to be built on it. The Flask framework uses Werkzeg as one of its bases.
jinja2
jinja2 is a popular template engine for Python.A web template system combines a template with a specific data source to render a dynamic web page.
This allows you to pass Python variables into HTML templates like this:
<html> <head> <title>{{ title }}</title> </head> <body> <h1>Hello {{ username }}</h1> </body> </html> |
Microframework
Flask is often referred to as a microframework. It is designed to keep the core of the application simple and scalable.
Flask supports extensions to add such capabilities to the application.
Why is Flask a good web framework choice?
Unlike the Django framework, Flask is very Pythonic. It’s easy to get started with Flask, because it doesn’t have a huge learning curve.
On top of that it’s very explicit, which increases readability. To create the “Hello World” app, you only need a few lines of code.
This is a boilerplate code example.
from flask import Flask app = Flask(__name__) def hello_world(): return 'Hello World!' if __name__ == '__main__': app.run() |
If you want to develop on your local computer, you can do so easily. Save this program as server.py and run it with python server.py.
$ python server.py * Serving Flask app "hello" * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit) |
It then starts a web server which is available only on your computer. In a web browser open localhost on port 5000 (the url) and you’ll see “Hello World” show up.
It’s a microframework, but that doesn’t mean your whole app should be inside one single Python file. You can and should use many files for larger programs, to handle complexity.
Micro means that the Flask framework is simple but extensible. You may all the decisions: which database to use, do you want an ORM etc, Flask doesn’t decide for you.
Flask is one of the most popular web frameworks, meaning it’s up-to-date and modern. You can easily extend it’s functionality. You can scale it up for complex applications.
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