io.ascii should name columns starting from 'col0' not 'col1'

When using astropy.io.ascii.read to read a file with no header, the columns are named by default as colX where X is a number starting from 1.

This is counter-intuitive to me, as Python reads indexes starting from zero. I would expect the first column to be named col0.

[astrofrog]

I wonder if we should keep a list somewhere of ‘known inconsistencies/sub-optimal APIs’ in case we ever develop new APIs? (without breaking old ones)

[hamogu]

I agree with @Gabriel-p that starting with col0 would be more in line with normal Python conventions, and is potentially confusing. Thanks a lot for pointing that out.

However, @pllim is absolutely right that this would potentially break user code in ways that may not lead to an exception but just silently produce wrong results. I wish we would have chosen 0 originally, but it’s not important enough to potentially break code now and thus I’m deciding to close this for now. Please add comments or re-open if you disagree.

(If you try tab["col0"] at least you’ll get an error so you know you need to check what’s going on.)