Install Flask 2.0.2

Flask is a web framework written in Python that lets you easily develop web applications. The two most popular frameworks for Python, Django and Flask, take incredibly different approaches to web development. Django, the older of the two frameworks, is often called a “batteries included” framework, meaning that it contains just about everything you need to launch a full featured application in no time flat. Flask, on the other hand, is a highly extensible “microframework” that launches with a bare minimum set of features, but has a thriving plugin ecosystem which allows developers to only include the functionality that they need to succeed.

Flask is based on the Werkzeug WSGI toolkit and the Jinja2 template engine and is considered very Pythonic, meaning it follows the conventions of the Python community and uses the language as intended. It’s explicit and readable.

Flask has the following dependencies, which will be installed automatically when installing Flask.

• Werkzeug, a utility library for WSGI. The WSBI protocol lets your web applications talk to the webserver and makes sure they work well together.
• Jinja2, a Python template engine used to create HTML, XML or other markup formats that are returned to the user via an HTTP response.
• MarkupSafe, which comes with Jinja2, escapes characters so text is safe to use in HTML and XML.
• ItsDangerous, which helps pass data to untrusted environments and to get it back safe and sound, in this case protecting Flask’s session cookie.
• Click, which is a tool for creating command line interfaces, and provides the flask command.

Installing Flask Globally

Copy (either ctrl+c or just click the “copy” button) and paste the snippet at the top of this page into your command line. As with all Python packages installed with Python’s default package manager, pip, Flask will be installed to %PYTHONHOME%/site-packages.

Installing Flask in a Virtual Environment

You can also work in a virtual environment to prevent conflicts. You can use pip to install a specific version of the Flask package into a virtual environment  for Python 3 projects with the following command:

python3 -m venv <path_to_env>

venv will create a virtual Python installation in the <env_name> folder.

Activate <env_name> with the following command:

On Linux

source <env_name>/bin/activate

On Windows

You can pip install Flask into your virtual environment with the following command:

python -m pip install flask

If you want to create a development server on your local computer, you can do so easily. Save your program as server.py and run it with python server.py.

For example:

$ python server.py
* Serving Flask app "hello"
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Flask makes it easy to build web applications since you can build a Flask application quickly using only a single Python file. It’s great for both beginner and complex use cases.

For example, you can create the “Hello World” application in your development environment as a simple Flask application with the following code:

from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello World!'
if __name__ == '__main__':
app.run()