Here are some popular online Python compilers that you can use to write, run, and test Python code:

1. **Repl.it** - [https://replit.com/](https://replit.com/)
- Supports multiple programming languages and includes a collaborative coding environment.

2. **Google Colab** - [https://colab.research.google.com/](https://colab.research.google.com/)
- Provides access to GPU and TPU resources, making it ideal for machine learning and data science projects.

3. **Programiz** - [https://www.programiz.com/python-programming/online-compiler/](https://www.programiz.com/python-programming/online-compiler/)
- Offers a simple interface with basic Python functionalities.

4. **OnlineGDB** - [https://www.onlinegdb.com/](https://www.onlinegdb.com/)
- Supports debugging, multiple languages, and has a beginner-friendly interface.

5. **PythonAnywhere** - [https://www.pythonanywhere.com/](https://www.pythonanywhere.com/)
- Good for running longer scripts and provides a simple, in-browser Python environment with free and paid plans.

6. **JDoodle** - [https://www.jdoodle.com/python3-programming-online/](https://www.jdoodle.com/python3-programming-online/)
- Has basic features for executing Python code and allows for easy sharing and collaboration.

These platforms vary in functionality, so you may choose one depending on your specific needs (like basic scripting vs. machine learning).