pandas 熊猫键盘错误
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Pandas Keyerror
提问by jincept
I have a very simple code:
我有一个非常简单的代码：
stats2 = {'a':[1,2,3,4,5,6],
'b':[43,34,65,56,29,76],
'c':[65,67,78,65,45,52],
'cac':['mns','ab','cd','cd','ab','k']}
f2 = pd.DataFrame(stats2)
f2.set_index(['cac'], inplace = True)
print(f2.ix['mns'])
print(f2['mns'])
f2.ix['mns'] works just fine. However, f2['mns'] reports KeyError. I am trying to understand why it does that. Is that how pandas work? Do I have to use ix even though I have set the index before?
f2.ix['mns'] 工作得很好。但是， f2['mns'] 报告 KeyError。我试图理解它为什么这样做。Pandas就是这样工作的吗？即使我之前设置了索引，我是否必须使用 ix？
回答by Nickil Maveli
This is your original dataframe:
这是您的原始数据框：
>>> df
a b c cac
0 1 43 65 mns
1 2 34 67 ab
2 3 65 78 cd
3 4 56 65 cd
4 5 29 45 ab
5 6 76 52 k
>>> df.set_index(['cac'], inplace=True)
>>> df
a b c
cac
mns 1 43 65
ab 2 34 67
cd 3 65 78
cd 4 56 65
ab 5 29 45
k 6 76 52
So, setting the index in pandas is simply replacing the before counter values(0,1,2,...,5) to the new row values i.e (mns, ab,...,k) of caccolumn name.
因此，在pandas 中设置索引只是将之前的计数器值(0,1,2,...,5) 替换为新的行值，即cac列名的(mns, ab,...,k) 。
>>> df.ix['mns']
a 1
b 43
c 65
This command specifically searches for row in the index column, cacwhose value is equal to mnsand retrieves it's corresponding elements.
该命令专门搜索索引列中的行，cac其值等于mns并检索其对应的元素。
Note:As mnsis not a column name of the dataframe, df['mns']throws a key error.
注意：由于mns不是数据df['mns']框的列名，会引发关键错误。
