访问这个蟒蛇熊猫系列的最后一个元素

Question

我有一个名为moving_average的蟒蛇熊猫系列。

moving_average = df['score'].rolling(window=period).mean()

我想检索系列moving_average的最后一个元素。这就是我所做的。

moving_average = df['score'].rolling(window=period).mean()[-1]

不幸的是，我收到了以下错误。

  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\series.py", line 601, in __getitem__
    result = self.index.get_value(self, key)
  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 2477, in get_value
    tz=getattr(series.dtype, 'tz', None))
  File "pandas\_libs\index.pyx", line 98, in pandas._libs.index.IndexEngine.get_value
  File "pandas\_libs\index.pyx", line 106, in pandas._libs.index.IndexEngine.get_value
  File "pandas\_libs\index.pyx", line 154, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 759, in pandas._libs.hashtable.Int64HashTable.get_item
  File "pandas\_libs\hashtable_class_helper.pxi", line 765, in pandas._libs.hashtable.Int64HashTable.get_item
KeyError: -1

我正在使用python v3.6

Answer 1

使用.iloc，否则Pandas会查找标记为-1的索引键，因为KeyError不存在。

moving_average = df['score'].rolling(window=period).mean().iloc[-1]

Answer 2

当您使用head()时，请不要忘记tail()

df['score'].rolling(window=period).mean().tail(1)

Answer 3

尝试：

moving_average = df['score'].rolling(window=period).mean().iloc[-1]

Answer 4

您可以使用：

moving_average = df['score'].rolling(window = period).mean().iloc[-1]