Definition of def, cdef and cpdef in cython

Question

I\'d like to know the difference between def, cdef and cpdef when I declare a function. The difference between def and the others it\'

Answer 1

def declares a function in Python. Since Cython is based on C runtime, it allows you to use cdef and cpdef.

cdef declares function in the layer of C language. As you know (or not?) in C language you have to define type of returning value for each function. Sometimes function returns with void, and this is equal for just return in Python.

Python is an object-oriented language. So you also can define class method in layer of C++ language, and override this methods in subclasses:

cdef class A:
    cdef foo(self):
        print "A"

cdef class B(A)
    cdef foo(self, x=None)
        print "B", x

cdef class C(B):
    cpdef foo(self, x=True, int k=3)
        print "C", x, k

Summary, why do we need to use def, cdef and cpdef? Because if you use Cython, your Python code will be converted into C code before compile. So with this things you can control the resulting C-code listing.

For more information I suggest you to read the official documentation: http://docs.cython.org/src/reference/language_basics.html