Common Mistakes Junior Developers Make with Flask and Their Potential Impacts

By hientd, at: 13:59 Ngày 10 tháng 7 năm 2024

Thời gian đọc ước tính: 8 min read

Common Mistakes Junior Developers Make with Flask and Their Potential Impacts
Common Mistakes Junior Developers Make with Flask and Their Potential Impacts

Common Mistakes Junior Developers Make with Flask and Their Potential Impacts

Flask is a popular micro web framework for Python that is simple yet powerful, making it a great choice for beginners and experienced developers alike. However, juniors often make some common mistakes due to many reasons. In this post, we'll explore these mistakes and discuss their potential impacts on your project.

 

1. Ignoring the Application Factory Pattern


Mistake

Many beginners start with a single-file application, which can quickly become unmanageable as the project grows. They often ignore the application factory pattern, which is essential for creating scalable and testable Flask applications.

Example:

# Single-file application
from flask import Flask

app = Flask(__name__)

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

 

Potential Impact

Ignoring the application factory pattern can lead to a tightly coupled and monolithic codebase, making it difficult to manage, test, and scale the application as it grows.

 

Correct Approach

# Using application factory pattern
def create_app():
    app = Flask(__name__)

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

    return app

 

 

2. Hardcoding Configuration Values


Mistake

Hardcoding configuration values directly in the code can lead to security issues and make it difficult to manage different environments (development, testing, production).

Example:

app.config['SECRET_KEY'] = 'hardcoded_secret_key'


Potential Impact

Hardcoding configuration values can expose sensitive information in your source code and make it challenging to configure the application for different environments without modifying the code. We can use Bandit as checker here.


Correct Approach

# config.py
import os

class Config:
    SECRET_KEY = os.environ.get('SECRET_KEY') or 'default_secret_key'

# app.py
from config import Config

app.config.from_object(Config)

 

 

3. Not Using Blueprints


Mistake

Neglecting the use of blueprints can lead to a disorganized codebase, especially for larger applications.

Example:

 
# Single monolithic file with all routes
@app.route('/route1')
def route1():
    pass

@app.route('/route2')
def route2():
    pass

 

Potential Impact

Without blueprints, the application can become cluttered and difficult to maintain as it grows, making it challenging to separate concerns and organize the code logically.
 

Correct Approach

# Using blueprints
from flask import Blueprint

bp = Blueprint('main', __name__)

@bp.route('/route1')
def route1():
    pass

@bp.route('/route2')
def route2():
    pass

# app.py
app.register_blueprint(bp)

 

4. Poor Error Handling


Mistake

Junior developers often overlook proper error handling, leading to unclear or insecure responses in case of failures.

Example:

@app.route('/data')
def data():
    item = get_item()
    return item.to_dict()


Potential Impact

Poor error handling can expose sensitive information, confuse users with unclear error messages, and make debugging and maintaining the application more difficult.


Correct Approach

@app.route('/data')
def data():
    try:
        item = get_item()
        return item.to_dict()
    except ItemNotFound:
        return {"error": "Item not found"}, 404
    except Exception as e:
        return {"error": str(e)}, 50

 

5. Not Using Flask Extensions


Mistake

Many juniors try to reinvent the wheel instead of using Flask extensions, which can handle common tasks efficiently and securely.

Example:

# Writing custom authentication middleware
@app.before_request
def authenticate():
    token = request.headers.get('Authorization')
    if not token:
        abort(401)


Potential Impact

Not using Flask extensions can lead to redundant and potentially insecure code, as well as missed opportunities to leverage community-vetted solutions for common tasks. Flask-owesome-libs is a great link to look at.

 

Correct Approach

# Using Flask-JWT-Extended for JWT authentication
from flask_jwt_extended import JWTManager

jwt = JWTManager(app)

# Configuration and initialization code

 

6. Ignoring Security Best Practices


Mistake

Ignoring security best practices, such as CSRF protection, input validation, and secure cookie handling, can lead to vulnerabilities.

Example:

@app.route('/submit', methods=['POST'])
def submit():
    data = request.form['data']
    process(data)

 

Potential Impact

Ignoring security best practices can expose the application to attacks such as cross-site scripting (XSS), cross-site request forgery (CSRF), and SQL injection, compromising the integrity and security of the application.


Correct Approach

# Using Flask-WTF for form handling and CSRF protection
from flask_wtf import FlaskForm
from wtforms import StringField
from wtforms.validators import DataRequired


class MyForm(FlaskForm):
    data = StringField('Data', validators=[DataRequired()])


@app.route('/submit', methods=['POST'])
def submit():
    form = MyForm()
    if form.validate_on_submit():
        process(form.data.data)
    return "Form submitted"

 

7. Improper Database Handling


Mistake

Not using SQLAlchemy or another ORM properly can lead to inefficient database interactions and potential SQL injection vulnerabilities.

Example:

# Executing raw SQL queries directly
@app.route('/user/<int:user_id>')
def user(user_id):
    result = db.engine.execute(f'SELECT * FROM users WHERE id={user_id}')
    user = result.fetchone()
    return user</int:user_id>

<int:user_id></int:user_id>

 

Potential Impact

Improper database handling can lead to inefficient queries, increased risk of SQL injection attacks, and difficulty in maintaining and scaling the database interactions within the application.

 

Correct Approach

# Using SQLAlchemy ORM - https://flask-sqlalchemy.palletsprojects.com/en/3.1.x/
@app.route('/user/<int:user_id>')
def user(user_id):
    user = User.query.get(user_id)
    return use</int:user_id>

<int:user_id></int:user_id>

 

8. Not Handling Static Files and Templates Properly


Mistake

Improperly serving static files and templates can lead to broken pages and inefficient loading.

Example:

# Hardcoding paths to static files
@app.route('/home')
def home():
    return ''

 

Potential Impact

Not handling static files and templates properly can result in broken images, styles, and scripts, leading to a poor user experience and increased maintenance efforts.

 

Correct Approach

# Using Flask's url_for to generate URLs for static files
@app.route('/home')
def home():
    image_url = url_for('static', filename='image.png')
    return f''

 

Conclusion

By being aware of these common mistakes and understanding their potential impacts, junior/fresher developers can build more robust, maintainable, and secure Flask applications. Remember to follow best practices and leverage the rich ecosystem of Flask extensions to streamline development and enhance your application's quality. 


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