Import non-integer constant in .pyx file

Question

How can I declare constants (of various types - not just enum values) and share them between multiple .pyx files?

Within a .pyx file, I can dec

Answer 1

You could use a very short inline function (in the pxd file) that just returns the constant

cdef inline const char* GetFavouriteFood():
    return "spam"

cdef inline float GetHowMuch():
    return 4.5

The other option would be to define the constants in C in a header file then (in your pxd) do

cdef extern from "myconstants.h":
   const char* FavouriteFood
   float HowMuch

The C compiler (rather than Cython) enforces the constness so errors will appear at that stage if you try to change them. This does involve create an extra file so personally I prefer the inline function approach.

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Edit (2018):

You can now include C code directly in Cython which makes the second approach easier:

cdef extern from *:
   """const char* FavouriteFood = "spam";
   const float HowMuch = 4.5;"""
   const char* FavouriteFood
   float HowMuch