For some data processing tasks Python can be brutally slow, especially text processing. NumPy is only fast because it's written in C and offloads hard numerical calculations to BLAS.
Yes but at least Python has very good native access to libraries.
For example I am sure Java is faster at numerical processing than pure Python at least with Python you have the option of writing in native. Python has really good C interop and it maybe considered by some not part of the language but I consider that it is.
Yeah you could write native code for Java via JNI but its not easy (granted its been a while) and for reasons I can't remember why but JNI is slow (probably moving stuff on and off the heap... I can't recall).
Decent, not very good. Ctypes is slow, cython requires extra boilerplate to become performant. Python/C API is even more annoying than that. (Compared even to something like JNI.)
