Best syntax I found so far:
import numpy
cimport numpy
cimport cython
@cython.boundscheck(False)
@cython.wraparound(False)
def primes(int kmax):
cdef int n, k, i
cdef numpy.ndarray[int] p = numpy.empty(kmax, dtype=numpy.int32)
k = 0
n = 2
while k < kmax:
i = 0
while i < k and n % p[i] != 0:
i = i + 1
if i == k:
p[k] = n
k = k + 1
n = n + 1
return p
Note where I used numpy.int32 instead of int. Anything on the left side of a cdef is a C type (thus int = int32 and float = float32), while anything on the RIGHT side of it (or outside of a cdef) is a python type (int = int64 and float = float64)