Question

我在Python中将决策树实现为词典。例如：

sampletree = {'spl':'foo', 'go_r':{'cut':150} ,  'l':{'val':100}, 'r':{'val':200}}

我有一个递归函数打印树：

def TREE_PRINT(tree, indent=''):
    #is this a leaf node?
    if 'val' in tree:
        print str(tree['val'])
    else:
        #print the criteria
        print 'split: '+ str(tree['spl']) + ' ' + str(tree['go_r'])
        #print the branches
        print indent+'L->', TREE_PRINT(tree['l'], indent+'  ')
        print indent+'R->', TREE_PRINT(tree['r'], indent+'  ')

如何抑制运行该功能时打印的无？

TREE_PRINT(sampletree)
split: foo {'cut': 150}
L-> 100
None
R-> 200
None

我试过返回''，但后来我得到了不必要的额外换行符。我正在构建编程集体智能中的第151页的'printtree'功能。

Answer 1

您的函数的返回值为None。不要打印函数的返回值 - 只需调用函数。

def TREE_PRINT(tree, indent=''):
    #is this a leaf node?
    if 'val' in tree:
        print str(tree['val'])
    else:
        #print the criteria
        print 'split: '+ str(tree['spl']) + ' ' + str(tree['go_r'])
        #print the branches
        print indent+'L->',
        TREE_PRINT(tree['l'], indent+'  ')

        print indent+'R->',
        TREE_PRINT(tree['r'], indent+'  ')

结果

split: foo {'cut': 150}
L-> 100
R-> 200

查看在线工作：ideone

Answer 2

您需要确定TREE_PRINT是否打印字符串表示或返回它。如果您的意思是它应该打印数据，那么您希望代码是：

def TREE_PRINT(tree, indent=''):
    #is this a leaf node?
    if 'val' in tree:
        print str(tree['val'])
    else:
        #print the criteria
        print 'split: '+ str(tree['spl']) + ' ' + str(tree['go_r'])
        #print the branches
        print indent+'L->',
        TREE_PRINT(tree['l'], indent+'  ')
        print indent+'R->',
        TREE_PRINT(tree['r'], indent+'  ')

用Python打印决策树的递归函数：抑制“无”

2 个答案: