astropy.io.ascii does not read pandas csv file correctly

Pandas by default will write CSV files where the header for the first column is missing:

In [4]: from pandas import DataFrame

In [5]: df = DataFrame()

In [6]: df['a'] = [1,2,3]

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

In [8]: %more test.csv
,a
0,1
1,2
2,3

Whether or not this is sensible is debatable, but this means there are a lot of CSV files in the wild missing the first header column name. Astropy doesn’t read these in correctly though:

In [10]: from astropy.io.ascii import read

In [11]: read('test.csv')
Out[11]: 
<Table masked=True length=4>
 col1 col2
int64 str1
----- ----
   --    a
    0    1
    1    2
    2    3

I think we might want to special case this, or deal better with cases like this given how common these kinds of files are going to be.

[drdavella]

@pllim, I don’t think it’s a bug. I think it’s the way that pandas indicates that the first column in a csv is an index, not a real data column. It’s possible to give the index column a name, but I believe it’s None by default. See the docs here:

https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.to_csv.html

[drdavella]

I could volunteer to look into this since I think I’d probably learn something new/useful. But if someone else already has a handle on a fix, that’s okay too.