arr = '[[1, 2], [3, 4], [5, 6]]' num_set = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0] arr_list = list(arr) matrix = [] row = [] for i in range(0, len(arr_list)): try: if(len(row) == 2): matrix.append(row) row = [] if(int(arr_list[i]) in num_set): row.append(int(arr_list[i])) except: continue print(matrix)