Of course! The "Cheetah" in the context of Python and Flask almost always refers to Cheetah, a mature and powerful templating language.
Let's break down what Cheetah is, how it works with Flask, and why you might (or might not) choose it.
What is Cheetah?
Cheetah is an open-source, template engine and code-generation tool for Python. Its primary goal is to separate presentation (HTML) from application logic (Python code).
Key Features of Cheetah:
- Python-like Syntax: Templates look very similar to Python code. This makes it easy for Python developers to learn.
- Reusability: You can define and reuse "def" (methods) and "set" (variables) within your templates.
- Inheritance: You can create a base template (a "skeleton") and have child templates extend it, overriding specific blocks. This is a cornerstone of modern web development.
- Dynamic Logic: You can embed Python loops, conditionals, and expressions directly into the template.
- Compilation: Cheetah templates are compiled into Python byte-code, which makes them very fast after the initial compilation.
How to Use Cheetah with Flask
Using Cheetah with Flask is straightforward. You just need to install the Cheetah library and tell Flask to use it as the template engine.
Step 1: Install Cheetah
First, you need to add Cheetah to your project's dependencies.
pip install Cheetah
Step 2: Configure Flask to Use Cheetah
By default, Flask looks for templates in a folder named templates and uses the Jinja2 engine. We need to change the default template folder and engine.
It's a common convention to use a templates-cheetah folder to avoid confusion with Jinja2 templates.
Here is a basic Flask app configured for Cheetah:
# app.py
from flask import Flask, render_template_string
# 1. Create the Flask app
app = Flask(__name__)
# 2. Configure Cheetah as the template engine
# We set a custom 'template_folder' to avoid conflict with Jinja2.
# We also tell Flask to use 'cheetah' as the template extension.
app.config['TEMPLATE_FOLDER'] = 'templates-cheetah'
app.config['TEMPLATES_AUTO_RELOAD'] = True # Good for development
app.template_folder = app.config['TEMPLATE_FOLDER']
app.jinja_env.add_extension('cheetah.ext.jinja2.CheetahExtension') # The magic line!
# --- Routes ---
@app.route('/')
def index():
# We will create this template in the next step
return render_template_string('''
#def greet(name)
Hello, $name!
#end def
#slurp
#include "header.html"
<h1>Welcome to the Homepage</h1>
<p>This is a Cheetah-powered Flask application.</p>
$greet("World")
#include "footer.html"
''')
@app.route('/user/<username>')
def user_profile(username):
# We will create this template in the next step
return render_template_string('''
#slurp
#include "header.html"
<h1>Profile for $username</h1>
#if len(username) > 5
<p>Your username is quite long!</p>
#else
<p>Your username is short and sweet.</p>
#end if
#include "footer.html"
''')
if __name__ == '__main__':
app.run(debug=True)
Explanation of the Configuration:
app.template_folder = 'templates-cheetah': This tells Flask to look for templates inside thetemplates-cheetahdirectory.app.jinja_env.add_extension(...): This is the most critical part. It registers Cheetah as an extension within Jinja2's environment. This allows you to use Cheetah's syntax (#def,#if,$variable) inside your templates, even though Flask's rendering system is technically running through Jinja2. This is the modern, recommended way to integrate Cheetah with Flask.
Step 3: Create the Template Files
Based on the render_template_string calls in our app.py, let's create the necessary files in the templates-cheetah directory.
File: templates-cheetah/header.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">Cheetah + Flask</title>
</head>
<body>
<header>
<h2>My Awesome Website</h2>
<nav>
<a href="/">Home</a> | <a href="/user/testuser">User Profile</a>
</nav>
</header>
<hr>
<main>
File: templates-cheetah/footer.html
</main>
<hr>
<footer>
<p>© 2025 Cheetah & Flask Demo</p>
</footer>
</body>
</html>
Step 4: Run the Application
Now, run your Flask application:
python app.py
Visit http://127.0.0.1:5000/ and http://127.0.0.1:5000/user/some_long_username to see your Cheetah templates in action!
Cheetah vs. Jinja2: Why Choose One Over the Other?
Flask's default template engine is Jinja2. It's powerful, fast, and has a massive community. So, why would you consider Cheetah?
| Feature | Cheetah | Jinja2 | Winner for Flask |
|---|---|---|---|
| Syntax | Python-like (#def, $var) |
Inspired by Django (, ) | Jinja2 (more common, cleaner) |
| Whitespace Control | #slurp directive, manual control |
Automatic, very powerful (, ) | Jinja2 (more elegant) |
| Inheritance | #extends and #block |
extends and block |
Tie (Both are excellent) |
| Speed | Very fast (compiled to Python) | Extremely fast (optimized in C) | Jinja2 (by a small margin) |
| Integration | Requires manual setup (as shown above) | Builtin, zero configuration | Jinja2 (by a huge margin) |
| Ecosystem | Smaller community, fewer resources | Massive community, vast plugins/tutorials | Jinja2 |
| Learning Curve | Easy for Python devs | Easy for Python devs | Tie |
When to Consider Cheetah:
- Legacy Projects: You are maintaining an old application that already uses Cheetah.
- Team Preference: Your team is already highly proficient with Cheetah and prefers its Pythonic syntax.
- Code Generation: Cheetah was designed as a general-purpose code generator, not just for HTML. It can be very effective for generating Python classes, configuration files, or SQL scripts.
When to Stick with Jinja2:
- 99% of new Flask projects. Jinja2 is the industry standard for a reason. It's better integrated, faster, has a more expressive syntax, and is what the entire Flask community uses. You will find far more help, tutorials, and pre-built template examples for Jinja2.
Conclusion
While it's absolutely possible to use Cheetah with Flask, it's important to understand that you are going against the grain. The setup is slightly more complex, and you are opting out of the rich ecosystem that surrounds Jinja2.
For any new project, Jinja2 is the recommended choice. Use Cheetah only if you have a specific, compelling reason to do so, such as integrating with existing legacy code.
