Pandas - 使用 to_csv 写入多索引行 [英] Pandas - write Multiindex rows with to_csv
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问题描述
我正在使用 to_csv 将多索引数据帧写入 csv 文件.csv 文件有一列包含元组中的多索引,例如:
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:
('a', 'x')
('a', 'y')
('a', 'z')
('b', 'x')
('b', 'y')
('b', 'z')
但是,我希望能够将 Multiindex 输出到两列而不是一列元组,例如:
However, I want to be able to output the Multiindex to two columns instead of one column of tuples, such as:
a, x
, y
, z
b, x
, y
, z
看起来 tupleize_cols
可以为列实现这一点,但对于行则没有这样的选项.有没有办法做到这一点?
It looks like tupleize_cols
can achieve this for columns, but there is no such option for the rows. Is there a way to achieve this?
推荐答案
我认为这样做
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
用索引重复来写(虽然有点黑客)
To write with the index duplication (kind of a hack though)
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
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
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