sqlite - How to avoid memory error in python when retrieving from database -

when try run code large amount of data, memoryerror in all_rows = [[x[0], x[1]] x in cur]. have 200m rows. how can avoid it?

binwidth = 1 latitudes = [] userids = [] info = [] densities = [] lite.connect(databasepath) con:     cur = con.execute('select latitude, userid dynamicmessage latitude>45')     print "executed"     all_rows = [[x[0], x[1]] x in cur]     all_rows = sorted(all_rows, key=itemgetter(0))     print "sorted"     x in all_rows:         latitudes.append(x[0])         userids.append(x[1])     min_lat = -100     max_lat = 100     binwidth = 1      bin_range = np.arange(min_lat,max_lat,binwidth)      binned_latitudes = np.digitize(latitudes,bin_range)     all_in_bins = zip(binned_latitudes,userids)     unique_in_bins = list(set(all_in_bins))     all_in_bins.sort()     unique_in_bins.sort()      bin_count_all = []     bin, group in groupby(all_in_bins, lambda x: x[0]):         bin_count_all += [(bin, len([k k in group]))]      bin_count_unique = []     bin, group in groupby(unique_in_bins, lambda x: x[0]):         bin_count_unique += [(bin, len([ k k in group]))]      bin_density = [(bin_range[b-1],a*1.0/u) ((b,a),(_,u)) in zip(bin_count_all, bin_count_unique)]      bin_density =  np.array(bin_density).transpose()      # all_in_bins , unique_in_bins contain data     # corresponding sql / pseudocode in question      # plot standard bar - note can put uneven widths in array-like here if necessary     plt.bar(*bin_density, width=binwidth)     plt.savefig('latlongstats'+'t'+str(time.strftime("%h:%m:%s")), format='png')