从 Pandas DataFrame 中采样一行后，如何获得一个单元格的值? [英] Once I sample a row from a pandas DataFrame, how can I get a value of one cell?

问题描述

我有一个 pandas DataFrame 并且我已经成功地从中采样了一行，但问题之一是它只是返回另一个 DataFrame.我需要读取返回的行并获取该行特定元素的值.

I have a pandas DataFrame and I've successfully sampled a row from it, but one of the problems is that it simply returns another DataFrame. I need to read the returned row and get the value of a particular element of that row.

我的 DataFrame 看起来像:

            Date        Open        High         Low       Close   Adj Close     Volume
0     1993-01-29   43.968700   43.968700   43.750000   43.937500   26.836645    1003200
1     1993-02-01   43.968700   44.250000   43.968700   44.250000   27.027504     480500
2     1993-02-02   44.218700   44.375000   44.125000   44.343700   27.084740     201300
3     1993-02-03   44.406200   44.843700   44.375000   44.812500   27.371080     529400
4     1993-02-04   44.968700   45.093700   44.468700   45.000000   27.485609     531500

我可以对一行进行采样:

I'm able to sample a row with:

start_state = self.market_data.iloc[:-self._num_trading_days_in_episode].sample(1)

最终看起来像:

            Date        Open        High         Low       Close   Adj Close     Volume
5299  2014-02-13  180.839996  183.199997  180.830002  183.009995  165.017517  100542200

现在我需要弄清楚如何从该行读取 Open 的值.

Now I need to figure out how to read the value of Open from that row.

推荐答案

使用:

start_state = self.market_data.iloc[:-self._num_trading_days_in_episode].sample(1)

首先可以通过通过标签选择DataFrame.loc 获取第一个索引值:

First is possible select by labels by DataFrame.loc with get first value of index:

open = start_state.loc[start_state.index[0], 'Open']
#faster alternative
#open = start_state.at[start_state.index[0], 'Open']

或者通过 DataFrame.iloc 和 Index.get_loc:

pos = market_data.columns.get_loc('Open')
open = start_state.iloc[0, pos]
#faster alternative
#open = start_state.iat[0, pos]

或者通过索引在numpy数组中选择第一个值:

Or select in numpy array first value by indexing:

open = start_state['Open'].values[0]
#pandas 0.24+
#open = start_state['Open'].to_numpy()[0]

或 Series.item 用于将一项 Series 转换为标量:

open = start_state['Open'].item()

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