Meritshot Tutorials
Flask Tutorial
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Introduction to Flask for Machine LearningIntroduction to Flask for Machine Learning
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Why Use Flask to Deploy ML Models?Why Use Flask to Deploy ML Models?
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Flask vs. Other Deployment Tools (FastAPI, Django, Streamlit)Flask vs. Other Deployment Tools (FastAPI, Django, Streamlit)
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Setting Up the EnvironmentSetting Up the Environment
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Basics of FlaskBasics of Flask
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Flask Application StructureFlask Application Structure
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Running the Development ServerRunning the Development Server
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Debug ModeDebug Mode
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Preparing Machine Learning Models for DeploymentPreparing Machine Learning Models for Deployment
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Saving the Trained ModelSaving the Trained Model
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Loading the Saved Model in PythonLoading the Saved Model in Python
Debug Mode
Debug mode is a powerful feature in Flask that helps developers test and debug their applications efficiently. It enables automatic reloading of the server whenever changes are made to the code and provides detailed error messages for troubleshooting.
Key Features of Debug Mode
- Automatic Code Reloading
- The server automatically restarts whenever changes are saved in the application code.
- Saves time as you don’t need to manually stop and restart the server.
- Detailed Error Messages
- Displays error tracebacks directly in the browser with interactive debugging tools.
- Allows you to explore the variables and context of the error for faster debugging.
How to Enable Debug Mode
There are two main ways to enable debug mode in Flask:
- By Setting the FLASK_ENV Variable
Set the FLASK_ENV environment variable to development.
For Windows (Command Prompt):
set FLASK_ENV=development
For Windows (PowerShell):
bash
Copy code
$env:FLASK_ENV = “development”
For macOS/Linux:
export FLASK_ENV=development
Once set, run the server using:
flask run
You will see the following in the terminal:
* Debug mode: on
- By Using the app.run() Method
You can enable debug mode directly in your Python code by passing the debug=True argument when running the Flask app.
Example:
from flask import Flask
app = Flask(__name__)
@app.route(“/”)
def home():
return “Welcome to Flask with Debug Mode!”
if __name__ == “__main__”:
app.run(debug=True)
Run the script using:
python app.py
Example: Debug Mode in Action
Consider this code snippet:
from flask import Flask
app = Flask(__name__)
@app.route(“/”)
def home():
return “Welcome to Flask!”
@app.route(“/error”)
def error():
# Intentional error for demonstration
return 1 / 0
if __name__ == “__main__”:
app.run(debug=True)
- Run the application with debug mode enabled.
- Navigate to http://127.0.0.1:5000/error.
- An error page will appear with a detailed traceback of the issue (ZeroDivisionError in this case), helping you locate the error.
Disabling Debug Mode
For production environments, debug mode must be turned off to avoid exposing sensitive information.
- Set FLASK_ENV to production:
set FLASK_ENV=production
- Or remove debug=True in the app.run() method.
Common Errors in Debug Mode
- Error: Debug Mode Not Enabled Despite Setting FLASK_ENV
- Cause: Flask version is outdated or python-dotenv is not installed.
- Fix: Update Flask and install python-dotenv:
pip install –upgrade flask python-dotenv
- Error: Interactive Debugger Not Displaying
- Cause: The browser does not support interactive debugging tools.
- Fix: Use a modern browser like Chrome, Firefox, or Edge.
Frequently Asked Questions
- Q: Why should I not use debug mode in production?
A: Debug mode reveals sensitive application details and provides an interactive debugger that can be exploited by malicious users. - Q: Can debug mode be enabled permanently?
A: Yes, you can set the FLASK_ENV=development variable in your environment configuration file to enable it permanently for development. - Q: Does debug mode affect application performance?
A: Debug mode may slightly impact performance because of automatic reloading and detailed error handling. Use it only during development. - Q: How do I know debug mode is enabled?
A: When you run flask run, the terminal will display:
* Debug mode: on
- Q: Can I use debug mode for multi-user testing?
A: Debug mode is intended for local testing by developers. For multi-user testing, deploy your app to a staging server without debug mode.
Debug mode is an indispensable tool for developers, enabling efficient testing and troubleshooting during the development process. By leveraging its features, you can quickly identify and resolve issues in your Flask applications.
