Python code crashes when running, but not when debugging (Ctypes) -

i running weird case little class involving ctypes writing. objective of class load matrix in proprietary format python structure had create (these matrices can have several cores/layers , each core/layer can have several indices refer few elements of matrix, forming submatrices).

the code test class this:

import numpy np reads_mtx import mtx import time  mymatrix=mtx()   mymatrix.load('d:\\mymatrix.mtx', true) 

and class created this:

import os import numpy np  ctypes import * import ctypes import time   def main():     pass   #a mydll mtx can have several cores #we need class define each core #and class hold whole file  class mtx_core:     def __init__(self):         self.name=none     #matrix core name         self.rows=-1       #number of rows in matrix         self.columns=-1    #number of columns in matrix         self.type=-1       #data type of matrix         self.indexcount=-1 #tuple number of indices each dimension         self.rindex={}     #dictionary indices rows         self.cindex={}     #dictionary indices columns         self.basedata=none         self.matrix=none       def add_core(self, mydll,mat,core):         namec=ctypes.create_string_buffer(50)         mydll.matrix_getlabel(mat,0,namec)         namec=repr(namec.value)         namec=namec[1:len(namec)-1]          #add information objects' methods         self.name=repr(namec)         self.rows= mydll.matrix_getbasenrows(mat)         self.columns=mydll.matrix_getbasencols(mat)         self.type=mydll.matrix_getdatatype(mat)         self.indexcount=(mydll.matrix_getnindices(mat,0 ),mydll.matrix_getnindices(mat,0 ))          #define data type numpy have according data type of matrix in question         dt=np.float64         v=(self.columns*c_float)()          if self.type==1:             dt=np.int32             v=(self.columns*c_long)()         if self.type==2:             dt=np.int64             v=(self.columns*c_longlong)()          #instantiate matrix         time.sleep(5)         self.basedata=np.zeros((self.rows,self.columns),dtype=dt)          #read matrix , puts in numpy array         in range(self.rows):             mydll.matrix_getbasevector(mat,i,0,self.type,v)             self.basedata[i,:]=v[:]           #reads indices rows , put them in dictionary         in range(self.indexcount[0]):             mydll.matrix_setindex(mat, 0, i)             v=(mydll.matrix_getnrows(mat)*c_long)()             mydll.matrix_getids(mat,0, v)             t=np.zeros(mydll.matrix_getnrows(mat),np.int64)             t[:]=v[:]             self.rindex[i]=t.copy()          #do same columns         in range(self.indexcount[1]):             mydll.matrix_setindex(mat, 1, i)             v=(mydll.matrix_getncols(mat)*c_long)()             mydll.matrix_getids(mat,1, v)             t=np.zeros(mydll.matrix_getncols(mat),np.int64)             t[:]=v[:]             self.cindex[i]=t.copy()    class mtx:     def __init__(self):         self.data=none         self.cores=-1         self.matrix={}         mydll=none      def load(self, filename, verbose=false):         #we load dll , initiate         mydll=cdll.loadlibrary('c:\\program files\\mysoftware\\matrixdll.dll')         mydll.initmatdll()          mat=mydll.matrix_loadfromfile(filename, true)          if mat<>0:             self.cores=mydll.matrix_getncores(mat)             if verbose==true: print "matrix has ", self.cores, " cores"             in range(self.cores):                 mydll.matrix_setcore(mat,i)                 namec=ctypes.create_string_buffer(50)                 mydll.matrix_getlabel(mat,i,namec)                 namec=repr(namec.value)                 namec=namec[1:len(namec)-1]                 #if verbose, list matrices being loaded                 if verbose==true: print "   loading core: ", namec                  self.datafile=filename                 self.matrix[namec]=mtx_core()                 self.matrix[namec].add_core(mydll,mat,i)         else:             raise nameerror('not possible open file. trancad returned '+ str(tc_value))           mydll.matrix_closefile(filename)         mydll.matrix_done(mat)   if __name__ == '__main__':     main() 

when run test code in form (double clicking, python's idle or pyscripter) crashes familiar error "windowserror: exception: access violation writing 0x0000000000000246", when debug code using pyscripter stoping in inner loop, runs perfectly.

i'd appreciate insights.

edit

the dumpbin output dll:

file type: dll

section contains following exports calipermtx.dll

00000000 characteristics 52fb9f15 time date stamp wed feb 12 08:19:33 2014     0.00 version        1 ordinal base       81 number of functions       81 number of names  ordinal hint rva      name        1    0 0001e520 initmatdll       2    1 0001b140 matrix_addindex       3    2 0001aee0 matrix_clear       4    3 0001ae30 matrix_closefile       5    4 00007600 matrix_copy       6    5 000192a0 matrix_createcache       7    6 00019160 matrix_createcacheex       8    7 0001eb10 matrix_createsimple       9    8 0001ed20 matrix_createsimplelike      10    9 00016d40 matrix_destroycache      11    00016da0 matrix_disablecache      12    b 0001a880 matrix_done      13    c 0001b790 matrix_dropindex      14    d 00016d70 matrix_enablecache      15    e 00015b10 matrix_getbasencols      16    f 00015b00 matrix_getbasenrows      17   10 00015ff0 matrix_getbasevector      18   11 00015ce0 matrix_getcore      19   12 000164c0 matrix_getcurrentindexpos      20   13 00015b20 matrix_getdatatype      21   14 00015ee0 matrix_getelement      22   15 00015a30 matrix_getfilename      23   16 00007040 matrix_getids      24   17 00015b80 matrix_getinfo      25   18 00015a50 matrix_getlabel      26   19 00015ae0 matrix_getncols      27   1a 00015ab0 matrix_getncores      28   1b 00016ec0 matrix_getnindices      29   1c 00015ac0 matrix_getnrows      30   1d 00018af0 matrix_getvector      31   1e 00015b40 matrix_iscolmajor      32   1f 00015b60 matrix_isfilebased      33   20 000171a0 matrix_isreadonly      34   21 00015b30 matrix_issparse      35   22 0001ae10 matrix_loadfromfile      36   23 0001bae0 matrix_new      37   24 00017150 matrix_openfile      38   25 000192d0 matrix_refreshcache      39   26 00016340 matrix_setbasevector      40   27 00015c20 matrix_setcore      41   28 00016200 matrix_setelement      42   29 00016700 matrix_setindex      43   2a 0001afa0 matrix_setlabel      44   2b 00018e50 matrix_setvector      45   2c 00005da0 mat_access_create      46   2d 00005e40 mat_access_createfromcurrency      47   2e 00004b10 mat_access_done      48   2f 00005630 mat_access_fillrow      49   30 000056d0 mat_access_fillrowdouble      50   31 00005a90 mat_access_getcurrency      51   32 00004c30 mat_access_getdatatype      52   33 000058e0 mat_access_getdoublevalue      53   34 00004c40 mat_access_getids      54   35 00005aa0 mat_access_getmatrix      55   36 00004c20 mat_access_getncols      56   37 00004c10 mat_access_getnrows      57   38 000055a0 mat_access_getrowbuffer      58   39 00005570 mat_access_getrowid      59   3a 00005610 mat_access_gettoreadflag      60   3b 00005870 mat_access_getvalue      61   3c 00005ab0 mat_access_isvalidcurrency      62   3d 000055e0 mat_access_setdirty      63   3e 000059f0 mat_access_setdoublevalue      64   3f 00005620 mat_access_settoreadflag      65   40 00005960 mat_access_setvalue      66   41 00005460 mat_access_useids      67   42 00005010 mat_access_useidsex      68   43 00005490 mat_access_useownids      69   44 00004d10 mat_access_validateids      70   45 0001e500 mat_pafree      71   46 0001e4e0 mat_palloc      72   47 0001e4f0 mat_pfree      73   48 0001e510 mat_prealloc      74   49 00006290 ma_mgr_addma      75   4a 00006350 ma_mgr_addmas      76   4b 00005f90 ma_mgr_create      77   4c 00006050 ma_mgr_done      78   4d 000060d0 ma_mgr_registerthreads      79   4e 00006170 ma_mgr_setrow      80   4f 00006120 ma_mgr_unregisterthread      81   50 0001e490 unloadmatdll 

summary

    6000 .data     5000 .pdata     c000 .rdata     1000 .reloc     1000 .rsrc    54000 .text