Access last element of this python panda Series

Question

I have a python panda series called moving_average.

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

I would like to retrieve the last element of Series moving_average. This is what I did.

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

Unfortunately, I got the following error.

  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

I am using python v3.6

Answer 1

Use .iloc, otherwise Pandas is looking for an index key labelled as -1 which doesn't exist hence the KeyError.

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

Answer 2

When you are using head() do not forget tail()

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

Answer 3

Try:

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

Answer 4

You can use:

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