IDEs with code completion and other features.

• Komodo - Multi-language IDE with support for Python 2.x and Python 3.x
• PyCharm - Free open-source IDE with a smart Python editor providing quick code navigation, code completion, refactoring, unit testing and debugger.
• WingIDE - Commercial Python IDE with advanced debugger, editor with vi, emacs, visual studio and other key bindings, auto-completion, auto-editing, snippets, goto-definition, find uses, refactoring, unit testing, source browser, and much more.
• NetBeans - Python/Jython support in NetBeans. Open source, allows Python and Jython Editing, code-completion, debugger, refactoring, templates, syntax analysis, etc.
• VS Tools for Python - Open-source plugin for Visual Studio 2010, 2012 and 2013. Supports syntax highlighting, debugging and rich intellisense, refactoring, object browser, MPI cluster debugging, Django intellisense and debugging, development REPL window and a debugging REPL window.
• Atom - 4th Generation enhanced GUI, rich integrated enviornmet for multiple languages including python.
• Visual Studio Code - Visual Studio Code is a lightweight but powerful source code editor which runs on your desktop and is available for Windows, macOS and Linux. It comes with built-in support for JavaScript, TypeScript and Node.js and has a rich ecosystem of extensions for other languages (such as C++, C#, Java, Python, PHP, Go) and runtimes (such as .NET and Unity).

Debugger

• pudb - A visual, console-based, full-screen debugger, designed as a more comfortable drop-in replacement for pdb.
• pyDebug - Debugger for Python programs with a graphical user interface.
• gdb - Windows Pyclewn allows using Vim as a front end to a debugger. Pyclewn currently supports gdb and pdb.

Testing

• pyUnit - Unit testing library for python.
• zopeTesting - Provides a powerful test runner that supports test discovery and a wide range of options to control how tests are run and results reported.
• quantifiedcode - for examine the code

Python Data Science Platform

• Anaconda - Anaconda is a an open source distribution of the Python and R programming languages and it is used in data science, machine learning, deep learning-related applications aiming at simplifying package management and deployment

Cloud IDEs for python

• pythonanywhere - Host, run, and code Python in the cloud: PythonAnywhere.
• cloud9 - Cloud9 combines a powerful online code editor with a full Ubuntu workspace in the cloud.
• codeanywhere - A complete toolset for web development. Enabling you to edit, collaborate and run your projects from any device.
• koding
• shiftedit - Free online IDE for web development with built-in FTP.
• pythonfiddle - The Python IDE for the web. Play around with and modify live example code. Share or demonstrate solutions to problems.
• codebunk