Build prerequisites for PyQwt-4.2.tar.gz on MacOS/X are:
The source package PyQwt-4.2.tar.gz contains the sources of the Qwt-4.2.0 library with a few patches. You have the option to compile and link those sources statically into PyQwt (easiest for most users).
However, the configure.py script lets you build PyQwt against a shared or static Qwt-4.2.0 library (not the 4.2.0rcX release candidates because of API enhancements).
To exploit the full power of the QwtPlot widget, you should install at least one the Numerical Python extensions: Numeric or its successor numarray. I am using Numeric-23.7.tar.gz and numarray-1.1.1.tar.gz. Versions of Numeric later than 21.0 are supported. Numarray is newer and therefore less stable than Numeric, so get the latest!