Code reuse is encouraged in most projects, independent of what language is being used. For large Python projects, access to a large codebase can generate very dense interconnections and this raises its own set of problems.
Main CVS tree is approx. 350 000+ lines of code. Supplementary trees have another 100 000 or so lines.
In a Python development environment, code reuse and sharing is easy and should be encouraged. Working out what a random piece of code does is often easier in Python than C or Java (to pick some examples), since there is less overhead involved in setting things up before the meat of the code.