CODEWITHSUNDEEP
cython
Colonel Panic
Colonel Panic

Reputation: 137662

What's wrong with my Cython?

I tried to write a Cython wrapper around the C++ library http://primesieve.org/

It wraps a single function count. So far, it installs correctly python setup.py install, but when I import primesieve the function primesieve.count is missing. Any ideas?

primesieve.pxd (following http://docs.cython.org/src/tutorial/clibraries.html)

cdef extern from "stdint.h":
    ctypedef unsigned long long uint64_t

cdef extern from "primesieve/include/primesieve.h":
    uint64_t primesieve_count_primes(uint64_t start, uint64_t stop)

primesieve.pyx

cimport primesieve

cpdef int count(self, int n):
    return primesieve.primesieve_count_primes(1, n)

setup.py

from setuptools import setup, Extension
from Cython.Build import cythonize

setup(
    ext_modules = cythonize([Extension("*", ["primesieve.pyx"], include_dirs = ["primesieve/include"])])
)

Upvotes: 3

Views: 285

Answers (1)

Richard Hansen
Richard Hansen

Reputation: 54213

Modify setup.py to link against libprimesieve.so by adding libraries = ["primesieve"] to you arguments to the Extension constructor. Without it, you'll get this error:

ImportError: ./primesieve.so: undefined symbol: primesieve_count_primes

Once I changed setup.py, it worked for me:

$ python2 setup.py build
...
$ (cd build/lib.linux-x86_64-2.7 && python2 -c 'import primesieve; print primesieve.count(None, 5)')
3

Upvotes: 2

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