如何解決我設計的解決決定因素的功能？

Question

該函數可以準確地計算1x1,2x2和3x3行列式，但它會給出高階行列式的錯誤值。我在思考函數中的部分存在問題，我稱之爲函數（遞歸）來解決低階行列式作爲解決方案的一部分。

我懷疑它與變量局部性有關，但我不確定爲什麼這會是一個問題，因爲我認爲局部性是自動的。

順便說一句，這是Python 2。

代碼：

def is_Det(matrix): 
    isdet = True 
    if not isinstance(matrix,list): # Is this actually a list? 
     isdet = False 
    for i in matrix: 
     if isinstance(i,list): # Things in matrix are lists? 
      if len(i) == len(matrix): # Square shape? 
       for j in i: # All numbers? 
        try: 
         j = float(j) 
        except ValueError: 
         isdet = False 
      else: 
       isdet = False 
     else: 
      isdet = False 
    return isdet 

def det_Disp(matrix): 
    if is_Det(matrix): 
     pass 
    else: 
     print "Error: Input not a determinant, cannot display" 

def det_Eval(matrix): 
    print matrix 
    except StandardError: 
     print "No such value" 
    if is_Det(matrix): 
     if len(matrix) == 1: # 1x1 determinant 
      print matrix[0][0] 
      return matrix[0][0] 
     elif len(matrix) == 2: # 2x2 determinant 
      print matrix[0][0] * matrix[1][1] - matrix[0][1] * matrix[1][0] 
      return matrix[0][0] * matrix[1][1] - matrix[0][1] * matrix[1][0] 
     else: 
      longdet = matrix # Expands higher-order determinant 
      for row1 in longdet: 
       for col1 in range(0,len(matrix)-1): 
        row1.append(row1[col1]) 
      value = 0 
      for col2 in range(0,len(matrix)): # Recurse determinant value 
       subdet = [] 
       for row2 in range(1,len(matrix)): 
        subsubdet = [] 
        for col3 in range(col2+1,col2+len(matrix)): 
         subsubdet.append(longdet[row2][col3]) 
        '''print "Subsubdet:", 
        print subsubdet #***************************''' 
        subdet.append(subsubdet) 
        '''# print "Subdet", 
        print "Subdet:", 
        print subdet #***************************''' 
       value += longdet[0][col2] * det_Eval(subdet) 
       ##########print value 
       '''#print longdet[1][col2], 
       #print det_Eval(subdet), 
       #print value 
      # print longdet''' 
      return value 
    else: 
     print "Error: Input not a determinant, cannot evaluate" 

#print det_Eval([[2,3],[4,9]]) 
#print det_Eval([[6,1,8],[9,9,9],[9,7,4]]) 
print det_Eval([[8,9,2,3],[4,6,1,8],[9,9,9,9],[1,9,7,4]]) 

Answer 1

在這一行處理未成年人：

value += longdet[0][col2] * det_Eval(subdet) 

你不採取標誌考慮 - sign depends on parity of index of the first line element（COL2）