I have a python script which I have transformed into a pyd file using Cython and Gcc. I would like it to be a black box, so that people cannot inspect it easily.
The source code after cythonization and compilation is hidden. However, it seems like you can still inspect it quite easily when you import the module in a python console and use the dir magic method. Is there a way to prevent code inspection from happening?
The first thing to emphasise is that Cython isn't really designed to help you hide your code - it's more an unintentional consequence. If Cython could get a 1% speed-up by making the source code for a compiled module completely visible then it'd probably choose to do that rather than hide it (however that's pretty unlikely... I can't see a mechanism that'd happen by).
Having some things visible by dir is pretty unavoidable. Cython is trying to make things behave like Python as far as possible and Python works by looking names up in a module dictionary. All dir does is print the keys from the module dictionary. However there are some things you can try:
cdef functions rather than def functions. cdef functions are only not callable (or visible) from Python. They have some limitations though - you can't use *args or **kwds as arguments for example. Some sub-notes:
cdef functions between modules then you will need to create a pxd file. shared cdef functions will appear in the __pyx_capi__ special attribute of your module where their name, C signature, and possibly function pointer will be able to anyone that looks.binding and embedsignature compiler directives will make regular def functions a little less easily introspected.cdef class with the cython.internal decorator. This makes it only easily accessible from within your module. Notes:
cdef classes aren't quite a substitute for Python classes (for example, all attributes must be pre-declared at compile-time),auto_pickle compiler directive.