Library should not be printing to stdout without verbose option

[jnothman]

I think it's good policy not to print anything to standard output in library code, except when that's specified by the API, e.g. through a verbose parameter. We have, for instance, a few unguarded print calls in sklearn/datasets. These should be weeded out. One option for fixing is to use logging.info; another is to use print(..., file=sys.stderr).

[fasiabbu]

Hi,
I see there are still a lot of places where print is being used. I presume all this should converted to logging.info. Is anybody working on this?

[lesteve]

@fasiabbu somebody is already working on this, look at the PR above i.e. #6930.

[amueller]

somewhat related #78

[mitar]

I would also prefer if all output would go through Python logging.

[jnothman]

Yes, this could do with some love. One concern is that we're not sure how to manage backwards compatibility.

[mitar]

Backwards compatibility being going to warn and print, or even the formatting of what has been printed out?

[jnothman]

More that current users may have code that expects stdout.​

[dkgaraujo]

It seems this is still open. One possibility to deal with users expecting prints to stdout is to append all existing prints with a deprecation warning, mentioning that in a next 1.x version the prints would be taken out and the user might adjust the verbose parameter (or whatever the other solution is).

[adrinjalali]

Closing as duplicate of #78