Message 258818 - Python tracker

Ok, the fix is now pushed to Python 2.7, 3.5 and 3.6.

Thanks Tijs Van Oevelen for your bug report ;-)

A workaround look to define the two lambda functions on two different lines. Or maybe cast explicitly to float? I don't think that it's a common bug so you should be able to survive with it until the next bugfix version is released :-)