Python：幫助提高遞歸函數

Question

我有以下函數，並且它不時地返回錯誤「全局名稱x未定義」，它在跳轉到return語句時發生。我希望幫助改進此代碼而不會丟失功能。任何有識之士將不勝感激。

def label(tree, instance, class_labels): 
    '''Returns the label at the end of every "branch" in the tree''' 
    global x 
    for row in tree: 
     if row[0] == instance[row[1]]: 
      if row[2][0] in class_labels: 
       x = row[2][0] 
       return x 
      else: 
       x = label(row[2], instance, class_labels) 
    return x 

Answer 1

這可以幫助...

def label(tree, instance, class_labels): 
    '''Returns the label at the end of every "branch" in the tree''' 
    last = None 
    for row in tree: 
     if row[0] == instance[row[1]]: 
      if row[2][0] in class_labels: 
       return row[2][0] 
      next = label(row[2], instance, class_labels) 
      if next is not None: 
       last = next 
    return last