Little trivial example of memory allocation and deallocation in cython with arrays, points, structs, and more...

Arrays of Cython Structs

from libc.stdlib cimport malloc, free, realloc

cdef struct Chair:
    int size

cdef class Bench:
    cdef Chair* chairs
    cdef readonly int num_chairs
    
    property chairs:

        def __get__(self):
            ret = []
            for i in range(self.num_chairs):
                ret.append(self.chairs[i].size)
            return ret
    
    def __cinit__(self):
        pass
    
    def add_some_chairs(self, int n):
        cdef Chair* chairs = <Chair *>malloc(n * sizeof(Chair))
        cdef int i = 0
        for i in range(n):
            chairs[i] = Chair(i)
            
        
        cdef int ret_type = self.add_chairs(chairs, n)
        free(chairs)
        if ret_type == 2:
            raise MemoryError("Could not allocate chairs")
        
    cdef int add_chairs(self, Chair[] chairs, int num_chairs) nogil:
        cdef int i, j
        cdef Chair * mem
        if num_chairs == 0:
            mem = <Chair * >malloc(num_chairs * sizeof(Chair))
            if mem != NULL:
                self.chairs = mem
                for i in range(num_chairs):
                    self.chairs[i] = chairs[i]
                return 1
            else:
                return 2
        else:
            mem = <Chair * >realloc(self.chairs, (self.num_chairs + num_chairs) * sizeof(Chair))
            if mem != NULL:
                self.chairs = mem
                j = 0
                for i in range(self.num_chairs, self.num_chairs + num_chairs):
                    self.chairs[i] = chairs[j]
                    j += 1
                self.num_chairs = self.num_chairs + num_chairs
                return 1
            else:
                return 2
            
    def __dealloc__(self):
        free(self.chairs)