Spyder
Scientific Python IDE. Open source. Aimed at data science + numeric computing. Standard part of the Anaconda distribution. Matlab-like interface with variable explorer, plot pane, console.
Pierre Raybaut started it in 2009 (then "Pydee"). Spyder 5 (2021) total UI modernization. User base: NumPy/SciPy/Matplotlib-heavy science workflows, academics. Competitors: Jupyter Notebooks (more mainstream, more interactive), PyCharm Scientific (commercial, more features), VS Code with Python extension (faster, more general). Spyder lives on in the Anaconda community + folks who want Matlab feel in Python.