IDLE (which comes with python) isn't that bad but it has the problem that by default it starts scripts in the same process itself runs in. this means that it crashes if the script causes an engine crash (like SED in debug mode :)). as far as i know this behaviour can be changed somehow but i forgot how so i use drpython at the moment. there are many other powerful editors for python but i like it simple.

since python code depends on proper indentation and mixed use of tabs and spaces is not good, it's important that the used editor can be set to either use tabs or spaces and doesn't make it too easy to mix both by mistake.

it for sure is possible. most languages make it possible to wrap c-libraries. writing wrappers by hand often is a lot of work though. i am no java expert and don't know what other tools exist but you could look into SWIG for example.