gmspro, 24.06.2012 10:42: > I see there are some files here started with underscore(_) , is there any convention of something for it? >> http://hg.python.org/cpython/file/3b7230997425/Modules >> _bisectmodule.c > [...] > _winapi.c >> Is there any convention or something? Yes. Please read the CPython developer guide (click on "core development" on the Python front page). Stefan