Python（Pandas）错误“标签[阿尔及利亚]不在[索引]中”
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Python (Pandas) error 'the label [Algeria] is not in the [index]'
提问by YohanRoth
I do not understand why this works
我不明白为什么这有效
df[(df['Gold']>0) & (df['Gold.1']>0)].loc[((df['Gold'] - df['Gold.1'])/(df['Gold'])).abs().idxmax()]
but when I divide by (df['Gold'] + df['Gold.1'] + df['Gold.2'])it stops working giving me error that you can find below.
但是当我除以(df['Gold'] + df['Gold.1'] + df['Gold.2'])它时，它停止工作，给我错误，你可以在下面找到。
Interestingly, the following line works
有趣的是，以下行有效
df.loc[((df['Gold'] - df['Gold.1'])/(df['Gold'] + df['Gold.1'] + df['Gold.2'])).abs().idxmax()]
I do not understand what is happening since I just started to learn Python and Pandas. I need to understand the reason why this happens and how to fix it.
我不明白发生了什么，因为我刚开始学习 Python 和 Pandas。我需要了解发生这种情况的原因以及如何解决。
ERROR
错误
KeyError: 'the label [Algeria] is not in the [index]'
KeyError: '标签 [Algeria] 不在 [index] 中'
DataFrame snap
数据帧快照
回答by jezrael
Your problem is boolean indexing:
你的问题是boolean indexing：
df[(df['Gold']>0) & (df['Gold.1']>0)]
returns a filtered DataFrame which does not contain the indexof maxvalue of Seriesyou calculated with this:
返回一个过滤后的数据帧，它不包含你用这个计算index的max值Series：
((df['Gold'] - df['Gold.1'])/(df['Gold'] + df['Gold.1'] + df['Gold.2'])).abs().idxmax()
In your data it is Algeria.
在您的数据中，它是Algeria.
So loclogically throws a KeyError.
所以loc逻辑上抛出一个KeyError.
One possible solution is to assign the new filtered DataFrameto df1and then get the index corresponding to the max value of Seriesby using idxmax:
一个可能的解决办法是赋予新的过滤DataFrame来df1，然后得到相应的最大值的指数Series使用idxmax：
df1 = df[(df['Gold']>0) & (df['Gold.1']>0)]
df2 = df1.loc[((df1['Gold']-df1['Gold.1'])/(df1['Gold']+df1['Gold.1']+df1['Gold.2'])).abs().idxmax()]
