scikit-learn: machine learning in Python

matplotlib: plotting with Python

The Web framework for perfectionists with deadlines.

A computer algebra system written in pure Python

The pytest framework makes it easy to write small tests, yet scales to support complex functional testing

Astronomy and astrophysics core library

An easy library for Python file locking. It works on Windows, Linux, BSD and Unix systems and can even perform distributed locking. Naturally it also supports the with statement.