How to Install Flask - Step-by-Step Installation Guide

How to Install Flask: A Beginner’s Guide

Flask is a popular lightweight web framework written in Python. It is known for its simplicity and flexibility, making it a favorite among developers who want to quickly build web applications.

Prerequisites

Python installed on your system (version 3.6 or higher recommended). You can download it from the official Python website.
Basic knowledge of the command line (Terminal on Mac/Linux, Command Prompt or PowerShell on Windows).
Optional but recommended: a virtual environment tool to keep your project dependencies isolated.

Step 1: Verify Python Installation

First, check if Python is installed and accessible from your command line.

python --version

Or on some systems:

python3 --version

If you see a Python version 3.x.x, you’re good to go. Otherwise, install Python as noted above.

Step 2: Create a Virtual Environment (Recommended)

Using a virtual environment helps manage packages for each project independently. Here’s how you can create one:

Navigate to your project folder or create one:

mkdir myflaskapp
cd myflaskapp

Create a virtual environment:

python -m venv venv

Activate the virtual environment:

On Windows:

venv\Scripts\activate

On Mac/Linux:

source venv/bin/activate

Step 3: Install Flask Using pip

With your virtual environment activated (or not if you skipped step 2), install Flask using pip:

pip install Flask

This command downloads and installs the latest Flask version from the Python Package Index.

Step 4: Verify Flask Installation

To confirm Flask installed correctly, run Python and try importing Flask:

python
>>> import flask
>>> print(flask.__version__)

If this prints the Flask version without errors, the installation was successful.

Step 5: Create a Simple Flask App

Let’s create a basic Flask application to test everything works:

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello():
    return "Hello, Flask!"

if __name__ == '__main__':
    app.run(debug=True)

Save this as app.py in your project directory.

Step 6: Run Your Flask Application

Run your app with this command:

python app.py

Visit http://127.0.0.1:5000/ in your web browser. You should see “Hello, Flask!” displayed.

Troubleshooting

pip not found: Ensure Python’s Scripts directory is in your system PATH or use python -m pip install Flask.
Virtual environment activation fails: Check your shell and OS-specific activation commands.
Permission errors: Avoid installing packages globally with sudo; use virtual environments.