python之为什么我得到 : "Length of values does not match length of index" error

我有以下代码，我正在尝试将 True 分配给一个新列，其中实际日期等于“D”列中的日期(创建日期)和 False 给任何其他人。

我是 Python 的新手，所以我想了解我做错了什么:

def GetData(): 
    myList = GetFileList(TodaysDate,5) 
    NewDataFrame  = pd.DataFrame() 
    for x in myList: 
        #The date of the actuals data is the day BEFORE it was created   
        ActualDate = getDate(x) - timedelta(days=1) 
 
        myTempData = pd.read_csv(WSIWeatherDir + "\\" + x, parse_dates = [" date"], date_parser = DateTimeParser) 
 
        myTempData = myTempData.replace(-99,np.nan) 
        myTempData = myTempData.loc[myTempData['name'].isin(NL_WeatherStations)] 
        myTempData['D'] = myTempData[' date'].dt.date 
 
        #MyData = myTempData.sort([' date'], ascending=True) 
        #print MyData 
 
        #Select indices of the weather file where the column " date" is equal to the actual date we are looking for 
        MyActualIndex = myTempData['D'] == ActualDate 
        MyActualData = myTempData[MyActualIndex] 
 
 
        MyExpectedIndex = myTempData.index.difference(MyActualData.index) 
        MyExpectedData =  myTempData.loc[MyExpectedIndex]  
 
        myTempData ['Actuals'] = [True] * len(MyActualData.index) 
        myTempData ['Actuals'] = [False] * len(MyExpectedData.index) 
 
        NewDataFrame = pd.concat([NewDataFrame,myTempData]) 
    return NewDataFrame 
print GetData() 

错误

runfile('C:/Users//Desktop/NLG_TAC_Calculation/TAC_2.py', wdir='C:/Users//Desktop/NLG_TAC_Calculation') 
Traceback (most recent call last): 
 
  File "<ipython-input-4-c9c151bca95a>", line 1, in <module> 
    runfile('C:/Users//Desktop/NLG_TAC_Calculation/TAC_2.py', wdir='C:/Users//Desktop/NLG_TAC_Calculation') 
 
  File "C:\Python27\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 685, in runfile 
    execfile(filename, namespace) 
 
  File "C:\Python27\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 71, in execfile 
    exec(compile(scripttext, filename, 'exec'), glob, loc) 
 
  File "C:/Users//Desktop/NLG_TAC_Calculation/TAC_2.py", line 117, in <module> 
    print GetData() 
 
  File "C:/Users//Desktop/NLG_TAC_Calculation/TAC_2.py", line 108, in GetData 
    myTempData ['Actuals'] = [True] * len(MyActualData.index) 
 
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 2127, in __setitem__ 
    self._set_item(key, value) 
 
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 2204, in _set_item 
    value = self._sanitize_column(key, value) 
 
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 2362, in _sanitize_column 
    value = _sanitize_index(value, self.index, copy=False) 
 
  File "C:\Python27\lib\site-packages\pandas\core\series.py", line 2579, in _sanitize_index 
    raise ValueError('Length of values does not match length of ' 
 
ValueError: Length of values does not match length of index 

请您参考如下方法:

我最好的猜测依赖于这部分:

myTempData ['Actuals'] = [True] * len(MyActualData.index) 
myTempData ['Actuals'] = [False] * len(MyExpectedData.index) 

它首先表示 myTempData['Actuals'] 是一个大小为 len(MyActualData.index) 的列，仅包含 True 值。接下来，它用包含 False 值的另一列大小 len(MyExpectedData.index)(我希望它会有所不同)替换所有内容。

您可以先创建一列 True 值，然后才替换 False 值:

myTempData['Actuals'] = True 
myTempData.iloc[MyExpectedIndex] = False