Based on Melissa O'Neill's paper, by way of incremental portings:

• Python2 to Python3
• Haskell to Python2
• Original paper, with Haskell implementation

This implementation presents a slightly simplified interface (with input validation) with support for skipping ahead and setting an upper bound. Python versions 2.7 and 3.4 through 3.7 are supported. A test suite is included. Support for 2.6 and 3.0 though 3.3 is expected, but not verified.

Pure Python. There are faster ways to do this.