I hadn't planned on doing a third beta of Coverage.py, but two things happened:

• I changed a number of details about the programmatic interface, and so wanted to get a little more verification that it's right.
• I discovered that the beta 2 kits weren't complete: the brand-new HTML reporting feature wouldn't work because the files were missing from the kit. Ugh.

So, beta 3 it is. Kits are available as source or as Windows installers from the coverage.py page on PyPI. The code is also available from the repository on bitbucket.

Feedback is welcome in any form you like, but particularly good ways are tickets on bitbucket, or email on the testing-in-python mailing list.

Significant changes in coverage.py since v2.x:

• HTML reports and annotation of source files: use the new -b (browser) switch. Thanks to George Song for code, inspiration and guidance.
• The trace function is implemented in C for speed. Coverage runs are now much faster. Thanks to David Christian for productive micro-sprints and other encouragement.
• Code in the Python standard library is not measured by default. If you need to measure standard library code, use the -L switch during execution.