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decision tree.py
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decision tree.py
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from collections import Counter
import pandas as pd
import random
import math
import copy
splitSign = ' ≤ '
# tested
def dataInit():
"""
初始化数据和属性集。
Returns: (数据, 属性集)
"""
Data = [['青绿', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.697, '好瓜'],
['乌黑', '蜷缩', '沉闷', '清晰', '凹陷', '硬滑', 0.774, '好瓜'],
['乌黑', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.634, '好瓜'],
['青绿', '蜷缩', '沉闷', '清晰', '凹陷', '硬滑', 0.608, '好瓜'],
['浅白', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.556, '好瓜'],
['青绿', '稍蜷', '浊响', '清晰', '稍凹', '软粘', 0.403, '好瓜'],
['乌黑', '稍蜷', '浊响', '稍糊', '稍凹', '软粘', 0.481, '好瓜'],
['乌黑', '稍蜷', '浊响', '清晰', '稍凹', '硬滑', 0.437, '好瓜'],
['乌黑', '稍蜷', '沉闷', '稍糊', '稍凹', '硬滑', 0.666, '坏瓜'],
['青绿', '硬挺', '清脆', '清晰', '平坦', '软粘', 0.243, '坏瓜'],
['浅白', '硬挺', '清脆', '模糊', '平坦', '硬滑', 0.245, '坏瓜'],
['浅白', '蜷缩', '浊响', '模糊', '平坦', '软粘', 0.343, '坏瓜'],
['青绿', '稍蜷', '浊响', '稍糊', '凹陷', '硬滑', 0.639, '坏瓜'],
['浅白', '稍蜷', '沉闷', '稍糊', '凹陷', '硬滑', 0.657, '坏瓜'],
['乌黑', '稍蜷', '浊响', '清晰', '稍凹', '软粘', 0.360, '坏瓜'],
['浅白', '蜷缩', '浊响', '模糊', '平坦', '硬滑', 0.593, '坏瓜']
# ['青绿', '蜷缩', '沉闷', '稍糊', '稍凹', '硬滑', 0.719, '坏瓜']
]
Attribute = ['色泽', '根蒂', '敲声', '纹理', '脐部', '触感', '密度']
IsDiscrete = [True, True, True, True, True, True, False]
return Data, Attribute, IsDiscrete
# tested
def generateDataFrame(Data, Attribute):
"""
将数据集转化为DataFrame类型。
Args:
Data (list): 数据集
Attribute (list): 属性集
Returns: DataFrame
"""
column = Attribute.copy()
column.append('类型')
frame = pd.DataFrame(Data, columns=column)
return frame
# tested
def getAttributeValue(Data, Attribute, IsDiscrete):
"""
统计所有离散属性的所有取值。
Args:
Data (): 数据集
Attribute (): 属性集
IsDiscrete (): 是否离散
Returns: 字典,所有离散属性的所有取值。例如:
{'色泽': {'乌黑', '青绿', '浅白'}, '根蒂': {'硬挺', '稍蜷', '蜷缩'}, '敲声': {'浊响', '沉闷', '清脆'},
'纹理': {'模糊', '清晰', '稍糊'}, '脐部': {'凹陷', '稍凹', '平坦'}, '触感': {'硬滑', '软粘'}}
"""
AttributeValue = {}
for i in range(len(IsDiscrete)):
if not IsDiscrete[i]: # 连续属性不统计取值
continue
tempSet = set()
for sample in Data:
tempSet.add(sample[i])
AttributeValue[Attribute[i]] = tempSet
return AttributeValue
# tested
def sameCategory(Data):
"""
判断是否所有数据均属于相同类型。
Args:
Data (list): 数据集
Returns: (类型, 是否相同)
"""
categories = [y[-1] for y in Data] # 数据集中的y向量(所有数据的标签)
return categories[0], len(set(categories)) == 1
# tested
def sameValue(Data):
"""
判断是否所有数据的所有属性值完全相同。
Args:
Data (list): 数据集
Returns: 是否相同
"""
xSet = set()
for sample in Data:
*x, y = sample
xSet.add(tuple(x))
return len(xSet) <= 1
# tested
def mostCategory(Data):
"""
获取数据中最主要的类别。
Args:
Data (list): 数据集
Returns: 最主要的类别(例如:“好瓜”)
"""
categories = [y[-1] for y in Data] # 数据集中的y向量(所有数据的标签)
return Counter(categories).most_common(1)[0][0]
# tested
def entropy(Data, Attribute):
frame = generateDataFrame(Data, Attribute)
pctofCategory = dict(frame['类型'].value_counts() / frame['类型'].value_counts().sum())
entropy = 0.0
for _, number in pctofCategory.items():
entropy -= number * math.log2(number)
return entropy
# tested
def informationGain(Data, Attribute, IsDiscrete, serlNum, dividingPoint=None):
"""
计算信息增益。
Args:
Data (): 数据集
Attribute (): 属性集
IsDiscrete (): 属性是否离散
serlNum (): 要计算信息增益的属性的下标
Returns: 信息增益
"""
frame = generateDataFrame(Data, Attribute)
ent = entropy(Data, Attribute)
gain = ent
if IsDiscrete[serlNum]:
AttrValues = set([sample[serlNum] for sample in Data])
dvSeries = frame[Attribute[serlNum]].value_counts()
for v in AttrValues:
dvNumber = dvSeries[v]
dvData = [sample for sample in Data if sample[serlNum] == v] # 取属性的某个值v的子数据集
gain -= dvNumber / len(Data) * entropy(dvData, Attribute)
else:
dvNumbers = [0, 0] # 第一项为小于划分点的数量,第二项为大于划分点的数量
for i in range(len(Data)):
dvNumbers[0 if Data[i][serlNum] < dividingPoint else 1] += 1
dvData1 = [sample for sample in Data if sample[serlNum] < dividingPoint]
dvData2 = [sample for sample in Data if sample[serlNum] >= dividingPoint]
gain = gain - dvNumbers[0] / len(Data) * entropy(dvData1, Attribute) - dvNumbers[1] / len(Data) * entropy(
dvData2, Attribute)
return gain
# tested
def getDividingPointList(continuousValues: pd.Series):
"""
获得所有候选划分点。
Args:
continuousValues (): 待划分的连续值序列
Returns:
list: 所有候选划分点
"""
sortedValues = continuousValues.sort_values().values.tolist()
DividingPointList = []
for i in range(continuousValues.size - 1):
DividingPointList.append((sortedValues[i] + sortedValues[i + 1]) / 2)
return DividingPointList
# tested
def bestAttribute(Data, Attribute, IsDiscrete):
"""
使用信息增益,获取最优化分属性和其在属性集中的下标。
Args:
Data (): 数据集
Attribute (): 属性集
Returns: (最优化分属性, 在属性集中的下标)
离散属性的最优划分属性是返回字符串
连续属性的最优划分属性是返回(属性名称, 划分点)
"""
gain = {} # {属性:信息增益},存储所有信息增益计算结果,连续属性取最大
frame = generateDataFrame(Data, Attribute)
dividingPoint = None # 连续值最佳划分点
for i, attr in enumerate(Attribute):
if IsDiscrete[i]:
gain[attr] = informationGain(Data, Attribute, IsDiscrete, i)
else:
gain[attr] = 0 # 连续值最佳信息增益
DividingPointList = getDividingPointList(frame[attr])
for dvdpt in DividingPointList:
tempGain = informationGain(Data, Attribute, IsDiscrete, i, dvdpt)
if tempGain > gain[attr]:
dividingPoint = dvdpt
gain[attr] = tempGain
gainlist = sorted(gain.items(), key=lambda x: x[1], reverse=True) # 降序排列所有信息增益
bestAttribute = gainlist[0][0]
# 在Attribute中查找bestAttribute的下标,再用下标在IsDiscrete中查找是否为离散属性
bestSerlNum = Attribute.index(bestAttribute)
if IsDiscrete[bestSerlNum]: # tested
return bestAttribute, bestSerlNum
else:
return (bestAttribute, dividingPoint), bestSerlNum
# tested
def simplifyData(DataofBAV, bestAttrSerl):
"""
将数据中对应最优划分属性的离散分量删除。
Args:
DataofBAV (): 数据
bestAttrSerl (): 要删除的下标
Returns: 列表,简化后的数据
"""
simplifiedData = DataofBAV.copy()
for sample in simplifiedData:
del sample[bestAttrSerl]
return simplifiedData
# tested
def addColumn(Data, serlNum, splitPoint):
"""
在数据集的末尾,为连续值的划分增加一列属性,True(小于等于)或False(大于)
Args:
serlNum (int): 属性的下标
splitPoint (float): 划分点
Data (list): 数据集
Returns:
返回增加了属性的数据集
"""
DataAdded = Data.copy()
for i, sample in enumerate(DataAdded):
DataAdded[i].append(sample[serlNum] <= splitPoint)
return DataAdded
# tested
def treeGenerate(Data, Attribute, IsDiscrete, AttributeValue):
"""
生成决策树。
Args:
IsDiscrete (list[bool]): 属性是否离散
AttributeValue (dict): 所有离散属性的所有取值
Data (list): 数据集
Attribute (list): 属性集
Returns: 决策树(字典)
"""
category, same = sameCategory(Data)
if same:
return category
if len(Attribute) == 0 or sameValue(Data):
return mostCategory(Data)
bestAttr, bestAttrSerl = bestAttribute(Data, Attribute, IsDiscrete)
# 递归过程中不修改原始数据集,属性集
DataCopy = copy.deepcopy(Data) # 包含子列表的完全复制
AttributeCopy = Attribute.copy()
IsDiscreteCopy = IsDiscrete.copy()
if isinstance(bestAttr, tuple): # 如果是连续属性,不需要增删AttributeCopy
attr, splitPoint = bestAttr
addColumn(DataCopy, bestAttrSerl, splitPoint) # 根据划分点统计,在数据末尾添加一列,True(<=)和False(>)
bestAttr = str(attr) + splitSign + str(splitPoint) # 整理成字符串形式('密度 ≤ 0.3815')
DecisionTree = {bestAttr: {}}
bestAttrSerl = -1 # 最佳属性为最后一列属性
BestAttrValues = [True, False]
for bestAttrValue in BestAttrValues:
DataofBAV = [sample for sample in DataCopy if sample[bestAttrSerl] == bestAttrValue]
if len(DataofBAV) == 0:
return mostCategory(DataCopy) # 返回D中样本最多的类
else:
DecisionTree[bestAttr][bestAttrValue] = treeGenerate(simplifyData(DataofBAV, bestAttrSerl),
AttributeCopy, IsDiscreteCopy, AttributeValue)
else:
if IsDiscreteCopy[bestAttrSerl]: # 离散属性选择之后即删除该属性,连续则不删
del AttributeCopy[bestAttrSerl]
del IsDiscreteCopy[bestAttrSerl]
DecisionTree = {bestAttr: {}}
BestAttrValues = AttributeValue[bestAttr] # 更换为一开始就生成的离散属性的所有取值,否则可能出现某一子树中缺取值,以至于无法分类的情况
for bestAttrValue in BestAttrValues:
DataofBAV = [sample for sample in DataCopy if sample[bestAttrSerl] == bestAttrValue]
if len(DataofBAV) == 0:
return mostCategory(DataCopy) # 返回D中样本最多的类
else:
DecisionTree[bestAttr][bestAttrValue] = treeGenerate(simplifyData(DataofBAV, bestAttrSerl),
AttributeCopy, IsDiscreteCopy, AttributeValue)
return DecisionTree
# tested
def classify(sample, Attribute, DecisionTree: dict):
"""
用决策树对单个数据分类。
Args:
sample (list): 单个数据
Attribute (): 属性集
DecisionTree (): 决策树
Returns:
分类结果
"""
if not isinstance(DecisionTree, dict): # 此时的DecisionTree即为分类结果
return DecisionTree
judgementPrinciple = tuple(DecisionTree.keys())[0]
try:
index = Attribute.index(judgementPrinciple)
except ValueError: # 找不到属性,说明是连续值(key中含有划分点信息)
judgementCategory, splitValue = judgementPrinciple.split(splitSign)
index = Attribute.index(judgementCategory)
value = sample[index]
# print(DecisionTree[judgementPrinciple][value <= float(splitValue)])
category = classify(sample, Attribute, DecisionTree[judgementPrinciple][value <= float(splitValue)])
else:
value = sample[index]
# print(DecisionTree[judgementPrinciple][value])
category = classify(sample, Attribute, DecisionTree[judgementPrinciple][value])
return category
# tested, abandoned
def removeListItem(originList, itemToRemove):
"""
去除列表中的特定项
Args:
originList (): 待删除的列表
itemToRemove (): 待删除的项
Returns:
删除后的列表
"""
for i in itemToRemove:
while i in originList:
originList.remove(i)
return originList
# tested
def dictToList(NestedDict: dict, itemToRemove=None):
"""
按深度由浅入深地将key记录在列表中,并返回列表。列表形式为['纹理', ('纹理', '稍糊', '触感'), ('纹理', '清晰', '密度 ≤ 0.3815')]。
Args:
itemToRemove (): 不希望放入list的key
NestedDict (dict): 待搜索的字典
Returns:
按深度由浅入深顺序的key的列表
"""
keyList = []
# 此时是根结点
for k1, v1 in NestedDict.items(): # 纹理,{稍糊:...,...}
keyList.append(k1)
for k2, v2 in v1.items(): # 稍糊,{敲声:...}
if v2 not in itemToRemove:
keyList.append((k1, k2, tuple(v2)[0])) # (纹理,稍糊,敲声),只取到前3层。
pointer = 1
while pointer <= len(keyList) - 1: # 每次层数深度+2
first = True
DisassembledDict = {} # 拆到当前层的字典,{沉闷:坏瓜,浊响:{脐部:...},...}
for k in keyList[pointer]:
if first:
DisassembledDict = NestedDict[k]
first = False
else:
DisassembledDict = DisassembledDict[k]
for k1, v1 in DisassembledDict.items(): # 沉闷,坏瓜;浊响,{脐部:...}
if isinstance(v1, dict): # 不需要else处理
for k2, v2 in v1.items(): # 脐部,{凹陷:坏瓜,...}
keyList.append(keyList[pointer] + (k1, k2))
pointer += 1
return keyList
# tested
def categoryCount(Data):
"""
计算数据集中各个类别的样本数。
Args:
Data (list): 数据集
Returns:
各个类别的样本数
"""
CategoryList = [y[-1] for y in Data]
return dict(Counter(CategoryList))
# tested
def shuffleSplit(Data, proportion):
"""
随机划分训练集 和 验证集或测试集。
Args:
proportion (): 训练集占数据集的比例
Data (): 数据集
Returns:
[训练集,验证集或测试集]
"""
# 按类别将Data分成一个字典,其key是类型,value是一个list,list的元素是该类的sample
CategoryList = [y[-1] for y in Data] # 数据集中的y向量(所有数据的标签)
CategorySet = set(CategoryList)
classifiedData = {c: [] for c in CategorySet}
for sample in Data:
classifiedData[sample[-1]].append(sample)
# 计算每个类别的数量,进而计算每个类别的要选取的数量(按proportion)
categoryNum = dict(Counter(CategoryList)) # {'好瓜': 8, '坏瓜': 8}
selectTrainNum = {c: int(n * proportion) for c, n in categoryNum.items()}
# 随机排序,顺序选择
TrainSet = []
TestingSet = []
for category, samples in classifiedData.items():
random.shuffle(samples)
TrainSet.extend(samples[0:selectTrainNum[category]])
TestingSet.extend(samples[selectTrainNum[category]:])
return TrainSet, TestingSet
# tested
def precision(TestingSet, Attribute, DecisionTree):
"""
计算分类精度。
Args:
TestingSet (): 测试集
Attribute (): 属性集
DecisionTree (): 决策树
Returns:
分类精度
"""
right = 0
for sample in TestingSet:
if classify(sample, Attribute, DecisionTree) == sample[-1]:
right += 1
return right / len(TestingSet)
def postpruning(TrainingSet, ValidationSet, Attribute, DecisionTree):
"""
对决策树后剪枝。
Args:
Attribute (): 属性集
TrainingSet (): 训练集
ValidationSet (): 验证集
DecisionTree (): 决策树
Returns:
是否剪枝了,完成后剪枝的决策树,剪枝后在验证集的精度。
"""
'''按深度由浅入深将key记录在列表中,形式为['纹理', ('纹理', '稍糊', '触感'), ('纹理', '清晰', '密度 ≤ 0.3815')]'''
DecisionList = dictToList(DecisionTree, list(set(y[-1] for y in Data))) #
'''建立一个字典TrainingNodeDict,其key为DecisionList中的值,value为到这个节点的各类型数量。
字典形式为{('纹理', '稍糊', '触感'):{'好瓜':2,'坏瓜':3}}'''
TrainingNodeDict = {}
for i, d in enumerate(DecisionList):
if i == 0:
categoryNum = categoryCount(TrainingSet)
TrainingNodeDict[d] = categoryNum
else:
TrainingSetCopy = copy.deepcopy(TrainingSet)
TrainingSetChosen = []
for j in range(int(len(d) / 2)):
if d[j * 2] in Attribute:
attrSerlNum = Attribute.index(d[j * 2])
TrainingSetChosen = [sample for sample in TrainingSetCopy if sample[attrSerlNum] == d[j * 2 + 1]]
else:
judgementCategory, splitValue = d[j * 2].split(splitSign)
splitValue = float(splitValue)
attrSerlNum = Attribute.index(judgementCategory)
TrainingSetChosen = [sample for sample in TrainingSetCopy if sample[attrSerlNum] <= splitValue]
TrainingSetCopy = TrainingSetChosen
categoryNum = categoryCount(TrainingSetChosen)
TrainingNodeDict[d] = categoryNum
'''倒序遍历,从最深的叶节点开始尝试剪枝。'''
pruned = False
finalPrecision = precision(ValidationSet, Attribute, DecisionTree) # 剪枝后在验证集的精度,初始值为剪枝前在验证集的精度
for d in reversed(DecisionList):
maxCategory = max(TrainingNodeDict[d], key=TrainingNodeDict[d].get) # 找到数量最多的类型
prunedTree = copy.deepcopy(DecisionTree)
ROI = prunedTree # 感兴趣部分,要修剪的部分。迭代后变成{'软粘': '好瓜', '硬滑': '坏瓜'}的形式。
if isinstance(d, tuple):
for k in d: # 例如:纹理,稍糊,触感
if k == d[-2]:
break
ROI = ROI[k]
ROI[d[-2]] = maxCategory # 不能一路走到想要的值,而是在最后一步使用直接改变的方式,否则无法起到指针的效果,而是类似复制的效果
else:
prunedTree = maxCategory
beforePrecision = precision(ValidationSet, Attribute, DecisionTree)
afterPrecision = precision(ValidationSet, Attribute, prunedTree)
if afterPrecision > beforePrecision:
DecisionTree = prunedTree
finalPrecision = afterPrecision
pruned = True
return pruned, DecisionTree, finalPrecision
def testCode():
# print(informationGain(Data, Attribute, IsDiscrete, 5))
# frame = generateDataFrame(Data, Attribute)
# print(frame.values.tolist())
# frame = generateDataFrame(Data, Attribute)
# DividingPointList = getDividingPointList(frame['密度'])
# print(DividingPointList)
# print(informationGain(Data, Attribute, IsDiscrete, 6, 0.3815))
# print(mostCategory(Data))
# print(sameCategory([[1, 2, 1], [7, 7, 1], [0, 8, 1], [8, 9, 's']]))
# print(bestAttribute(Data, Attribute, IsDiscrete))
# DataofBAV = [['青绿', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.697, '好瓜'],
# ['乌黑', '蜷缩', '沉闷', '清晰', '凹陷', '硬滑', 0.774, '好瓜'],
# ['乌黑', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.634, '好瓜'],
# ['青绿', '蜷缩', '沉闷', '清晰', '凹陷', '硬滑', 0.608, '好瓜'],
# ['浅白', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.556, '好瓜'],
# ['青绿', '稍蜷', '浊响', '稍糊', '凹陷', '硬滑', 0.639, '坏瓜'],
# ['浅白', '稍蜷', '沉闷', '稍糊', '凹陷', '硬滑', 0.657, '坏瓜']
# ]
# bestAttrSerl = 4
# print(simplifyData(DataofBAV, bestAttrSerl))
# print(addColumn(Data, 6, 0.6))
# print(classify(['青绿', '蜷缩', '沉闷', '稍糊', '稍凹', '硬滑', 0.719], Attribute, DecisionTree))
# print(classify(['青绿', '蜷缩', '沉闷', '清晰', '稍凹', '硬滑', 0.3815], Attribute, DecisionTree))
# print(classify(['乌黑', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.634], Attribute, DecisionTree))
# print(classify(['乌黑', '稍蜷', '浊响', '稍糊', '稍凹', '软粘', 0.481], Attribute, DecisionTree))
# print(removeListItem(['好瓜', '坏瓜', {'key1': 'value1', 'key2': {'key1': 'value1'}}, '其它', '坏瓜'], ['好瓜', '坏瓜']))
# print(dictToList(DecisionTree, ['好瓜', '坏瓜']))
# TrainingSet = [['浅白', '硬挺', '清脆', '模糊', '平坦', '硬滑', 0.245, '坏瓜'], ['乌黑', '稍蜷', '浊响', '清晰', '稍凹', '软粘', 0.36, '坏瓜'], ['浅白', '蜷缩', '浊响', '模糊', '平坦', '软粘', 0.343, '坏瓜'], ['青绿', '硬挺', '清脆', '清晰', '平坦', '软粘', 0.243, '坏瓜'], ['浅白', '稍蜷', '沉闷', '稍糊', '凹陷', '硬滑', 0.657, '坏瓜'], ['乌黑', '稍蜷', '沉闷', '稍糊', '稍凹', '硬滑', 0.666, '坏瓜'], ['乌黑', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.634, '好瓜'], ['乌黑', '稍蜷', '浊响', '清晰', '稍凹', '硬滑', 0.437, '好瓜'], ['浅白', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.556, '好瓜'], ['乌黑', '稍蜷', '浊响', '稍糊', '稍凹', '软粘', 0.481, '好瓜'], ['青绿', '蜷缩', '沉闷', '清晰', '凹陷', '硬滑', 0.608, '好瓜'], ['青绿', '稍蜷', '浊响', '清晰', '稍凹', '软粘', 0.403, '好瓜']]
# TestingSet = [['浅白', '蜷缩', '浊响', '模糊', '平坦', '硬滑', 0.593, '坏瓜'], ['青绿', '稍蜷', '浊响', '稍糊', '凹陷', '硬滑', 0.639, '坏瓜'], ['青绿', '蜷缩', '浊响', '清晰', '凹陷', '硬滑', 0.697, '好瓜'], ['乌黑', '蜷缩', '沉闷', '清晰', '凹陷', '硬滑', 0.774, '好瓜']]
# DecisionTree = {'密度 ≤ 0.3815': {True: '坏瓜', False: {'密度 ≤ 0.6455': {True: '好瓜', False: '坏瓜'}}}}
pass
if __name__ == '__main__':
Data, Attribute, IsDiscrete = dataInit()
AttributeValue = getAttributeValue(Data, Attribute, IsDiscrete)
# DecisionTree = treeGenerate(Data, Attribute, IsDiscrete, AttributeValue)
# print(DecisionTree)
TrainingSet, TestingSet = shuffleSplit(Data, 0.75)
print('训练集:{0}\n验证集:{1}'.format(TrainingSet, TestingSet))
DecisionTree = treeGenerate(TrainingSet, Attribute, IsDiscrete, AttributeValue)
print('决策树:', DecisionTree)
print('训练集上精度:', precision(TrainingSet, Attribute, DecisionTree))
print('验证集上精度:', precision(TestingSet, Attribute, DecisionTree))
pruned, DecisionTree, finalPrecision = postpruning(TrainingSet, TestingSet, Attribute, DecisionTree)
if pruned:
print('后剪枝后的决策树:', DecisionTree)
print('后剪枝后在训练集上的精度:', precision(TrainingSet, Attribute, DecisionTree))
print('后剪枝后在验证集上的精度:', finalPrecision)