Python pyjwt Module: Detailed Guide to Advanced Features and Installation

Python Modules › Web Development
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Python pyjwt Module

The pyjwt module is a Python library that allows developers to encode and decode JSON Web Tokens (JWTs). This module provides a flexible way of handling authentication and authorization in applications. Using JWTs, developers can securely transmit information as a JSON object, ensuring the integrity and authenticity of the information through signing and verification processes. The pyjwt library is compatible with Python 3.6 and above.

Module Introduction

The pyjwt module is designed for creating and verifying JSON Web Tokens. It supports various algorithms for signing tokens, making it a versatile tool for securing APIs and applications. It fully conforms to the JWT standards outlined in RFC 7519 and provides a straightforward API for integrating JWT into your Python projects.

Application Scenarios

The pyjwt module is invaluable in scenarios where secure, token-based authentication is necessary. It is commonly used in:

  • Web Applications: To provide JWT-based authentication mechanisms for users logging in and maintaining sessions.
  • Microservices: To enable secure communication between microservices with each service validating JWT tokens for access control.
  • Single Page Applications (SPAs): To manage user sessions without needing to constantly send authentication credentials.

Installation Instructions

The pyjwt module is not included in the Python standard library, so it requires installation. You can easily install it via pip with the following command:

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pip install PyJWT

Usage Examples

Example 1: Creating a JWT Token

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import jwt  # Import the jwt module for encoding and decoding tokens
import datetime  # Import datetime for setting token expiration time

# Define a secret key for signing the token
secret_key = 'your_secret_key'  
# Create a payload containing user information and token expiration
payload = {
    'user_id': 123,  # The user's ID
    'exp': datetime.datetime.utcnow() + datetime.timedelta(seconds=30)  # Token will expire in 30 seconds
}

# Encode the payload to create a JWT
token = jwt.encode(payload, secret_key, algorithm='HS256')  # Use HS256 algorithm to sign the token
print(token)  # Print the generated token

Example 2: Decoding a JWT Token

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try:
    # Decode the token to extract the payload
    decoded_payload = jwt.decode(token, secret_key, algorithms=['HS256'])  # Specify the same algorithm used for encoding
    print(decoded_payload)  # Print the decoded payload
except jwt.ExpiredSignatureError:
    print('Token has expired!')  # Handle expired tokens
except jwt.InvalidTokenError:
    print('Invalid token!')  # Handle invalid tokens

Example 3: Using JWT in an API with Flask

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from flask import Flask, request, jsonify  # Import necessary Flask components
import jwt  # Import jwt for handling JWTs
import datetime  # Import datetime for token expiration

app = Flask(__name__)  # Create a Flask application
secret_key = 'your_secret_key'  # Define the secret key for signing tokens

@app.route('/login', methods=['POST'])  # Define a route for logging in
def login():
    data = request.json  # Get JSON data from request
    # Simplified user validation
    if data['username'] == 'test' and data['password'] == 'password':  
        payload = {
            'user_id': 1,  # Simulated user ID
            'exp': datetime.datetime.utcnow() + datetime.timedelta(minutes=30)  # Token valid for 30 min
        }
        token = jwt.encode(payload, secret_key, algorithm='HS256')  # Generate token
        return jsonify({'token': token})  # Send the token in response
    return jsonify({'message': 'Invalid credentials'}), 401  # Return error for invalid credentials

@app.route('/protected', methods=['GET'])  # Define a protected route
def protected():
    token = request.headers.get('Authorization')  # Get token from Authorization header
    try:
        decoded_payload = jwt.decode(token, secret_key, algorithms=['HS256'])  # Decode the token
        return jsonify({'message': 'Protected route accessed!', 'user_id': decoded_payload['user_id']})  # Access granted
    except jwt.ExpiredSignatureError:
        return jsonify({'message': 'Token has expired!'}), 401  # Handle expired token
    except jwt.InvalidTokenError:
        return jsonify({'message': 'Invalid token!'}), 401  # Handle invalid token

if __name__ == '__main__':
    app.run(debug=True)  # Run the Flask application

Software and library versions are constantly updated

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