Cython: how to return a function in Cython
I need a cythonize function that takes lenscale and sigvar parameters in order to build a function. I would like to be able to do this without doing the k_se class. When I run the following code:
ctypedef float (*kfunc)(float, float)
cdef kfunc k_se(float lenscale, float sigvar):
cdef float f(float xi, float xj):
return sigvar**2. * _np.exp(-(1./(2. * lenscale**2.)) *\
_npl.norm(xi - xj)**2)
return f
I am getting the error:
Error compiling Cython file:
------------------------------------------------------------
...
cdef kfunc k_se(float lenscale, float sigvar):
cdef float f(float xi, float xj):
^
------------------------------------------------------------
BUILDGP.pyx:15:36: C function definition not allowed here
I also tried this, trying to return a lambda that cython could not compile either. Any ideas if I should create a constructor class for the k_se functions?
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jbbj94
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1 answer
You can create a class that can be initialized with a set of parameters and acts like a callable:
class Function():
def __init__(self, float lenscale):
self.lenscale = lenscale
def __call__(self, float xi):
return self.lenscale*xi
f = Function(10)
print f(5)
The cython documentation has more details on this.
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David Zwicker
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