7

prob in the title. exaple:

x=[('a','a','c') for i in range(5)]
df = DataFrame(x,columns=['col1','col2','col3'])
df.to_csv('test.csv')
df1 = read_csv('test.csv')

   Unnamed: 0 col1 col2 col3
0           0    a    a    c
1           1    a    a    c
2           2    a    a    c
3           3    a    a    c
4           4    a    a    c

The reason seems to be that when saving a dataframe, the index column is written also, with no name in the header. then when you load the csv again, it is loaded with the index column as unnamed column. Is this a bug? How can I avoid writing a csv with the index, or dropping unnamed columns in reading?

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4 Answers 4

Reset to default
8

You can remove row labels via the index and index_label parameters of to_csv.

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1 Comment

This is what I was looking for, as it avoid creating the problem instead of handling afterwords.
6

These are not symmetric as there are ambiguities in the csv format because of the positioning. You need to specify an index_col on read-back

In [1]: x=[('a','a','c') for i in range(5)]

In [2]: df = DataFrame(x,columns=['col1','col2','col3'])

In [3]: df.to_csv('test.csv')

In [4]: !cat test.csv
,col1,col2,col3
0,a,a,c
1,a,a,c
2,a,a,c
3,a,a,c
4,a,a,c

In [5]: pd.read_csv('test.csv',index_col=0)
Out[5]: 
  col1 col2 col3
0    a    a    c
1    a    a    c
2    a    a    c
3    a    a    c
4    a    a    c

This looks very similar to the above, so is 'foo' a column or an index?

In [6]: df.index.name = 'foo'

In [7]: df.to_csv('test.csv')

In [8]: !cat test.csv
foo,col1,col2,col3
0,a,a,c
1,a,a,c
2,a,a,c
3,a,a,c
4,a,a,c
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2 Comments

Thanks, I thought the solution would be simple :)
it is, just specify index_col=0
0

You can specify explicitly which columns you want to write using cols parameter.

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1 Comment

That is not good, as i might have many, many columns.. what i can do though is df[df.columns].to_csv(). that wouldnt be a big trouble..
0

That s how use index df.to_csv('test.csv', index_label=False) But for me, when I've tried submit to Kaggle it's return error "ERROR: Record 1 had 3 columns but expected 2", so I solved it use this code.

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1 Comment

You should consider adding some explanatory text to your answer to increase its quality.

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