在 Python 中打印决策树的递归函数：抑制“无”

发布于 2024-12-19 10:58:10 字数 775 浏览 1 评论 0原文

我将决策树作为字典在 Python 中实现。示例：

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+'  ')

如何抑制运行该函数时打印的 None ？

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

我尝试返回 ''，但随后出现了不需要的额外换行符。我正在基于《集体智能编程》第 151 页中的“printtree”函数进行构建。

原文

I decision trees implemented in Python as dictionaries. Example:

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

I have a recursive function prints the tree:

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+'  ')

How do I suppress the None's that are printed when I run the function?

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

I tried returning '', but then I get line unwanted extra line breaks.
I'm building off of the 'printtree' function from page 151 in Programming Collective Intelligence.

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荒路情人 2024-12-26 10:58:10

你的函数的返回值是None。不要打印函数的返回值 - 只需调用您的函数。

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

查看它在线运行：ideone

The return value of your function is None. Don't print the return value of your function - just call your function.

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+'  ')

Result

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

See it working online: ideone

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梦年海沫深 2024-12-26 10:58:10

您需要决定 TREE_PRINT 是打印字符串表示形式还是返回它。如果您的意思是它应该打印数据，那么您想要的代码是：

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+'  ')

You need to decide if TREE_PRINT prints the string representation or returns it. If you mean that it should print the data, then what you want your code to be is:

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+'  ')

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