Pandas - 使用 to_csv 写入多索引行
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Pandas - write Multiindex rows with to_csv
提问by
I am using to_csv to write a Multiindex DataFrame to csv files. The csv file has one column that contains the multiindexes in tuples, like:
我正在使用 to_csv 将 Multiindex DataFrame 写入 csv 文件。csv 文件有一列包含元组中的多索引，例如：
('a', 'x')
('a', 'y')
('a', 'z')
('b', 'x')
('b', 'y')
('b', 'z')
However, I want to be able to output the Multiindex to two columns instead of one column of tuples, such as:
但是，我希望能够将 Multiindex 输出到两列而不是一列元组，例如：
a, x
, y
, z
b, x
, y
, z
It looks like tupleize_colscan achieve this for columns, but there is no such option for the rows. Is there a way to achieve this?
看起来tupleize_cols可以为列实现这一点，但行没有这样的选项。有没有办法实现这一目标？
采纳答案by Jeff
I think this will do it
我认为这会做到
In [3]: df = DataFrame(dict(A = 'foo', B = 'bar', value = 1),index=range(5)).set_index(['A','B'])
In [4]: df
Out[4]:
value
A B
foo bar 1
bar 1
bar 1
bar 1
bar 1
In [5]: df.to_csv('test.csv')
In [6]: !cat test.csv
A,B,value
foo,bar,1
foo,bar,1
foo,bar,1
foo,bar,1
foo,bar,1
In [7]: pd.read_csv('test.csv',index_col=[0,1])
Out[7]:
value
A B
foo bar 1
bar 1
bar 1
bar 1
bar 1
To write with the index duplication (kind of a hack though)
用索引重复写入（虽然有点黑客）
In [27]: x = df.reset_index()
In [28]: mask = df.index.to_series().duplicated()
In [29]: mask
Out[29]:?
A ? ?B ?
foo ?bar ? ?False
? ? ?bar ? ? True
? ? ?bar ? ? True
? ? ?bar ? ? True
? ? ?bar ? ? True
dtype: bool
In [30]: x.loc[mask.values,['A','B']] = ''
In [31]: x
Out[31]:?
? ? ?A ? ?B ?value
0 ?foo ?bar ? ? ?1
1 ? ? ? ? ? ? ? ?1
2 ? ? ? ? ? ? ? ?1
3 ? ? ? ? ? ? ? ?1
4 ? ? ? ? ? ? ? ?1
In [32]: x.to_csv('test.csv')
In [33]: !cat test.csv
,A,B,value
0,foo,bar,1
1,,,1
2,,,1
3,,,1
4,,,1
Read back is a bit tricky actually
回读实际上有点棘手
In [37]: pd.read_csv('test.csv',index_col=0).ffill().set_index(['A','B'])
Out[37]:
value
A B
foo bar 1
bar 1
bar 1
bar 1
bar 1
