Use `logging` module instead of outputting to `stdout` about pycma

[nikohansen]

Thanks for noticing. There is not specific reason apart from ignorance of the existence of the logging module at the time of coding. I'll be happy to consider your PR!

[truenicoco]

Thanks for answering. I've already done some very minor and ugly modifications for my own use, I'll consider removing all the prints out there, in a clean way.

[nikohansen]

Playing around with the logging module (I find the documentation slightly too complicated). The caveats I have so far: logging.info prints on red background, which I don't like for generic output messages. Is there a simple way to change this? This recommends to use warnings.warn when the client code should try to prevent the warning. I can see that the logging module is quite useful for debug, error and some warning messages.

[truenicoco]

logging outputs to stderr by default. I think it should be up to the user to decide if this is fine with him, or if he wants it in file, or in stdout.; this is one of the reasons why this standard module is great IMHO.

However, the link you provided also states that print() should be used to

Display console output for ordinary usage of a command line script or program

To do things pythonicly and neatly, I think it would be OK for "interactive shell usage" or a command-line interface to uses prints. However, when used as a module from another script, pycma should use warnings.warn and logging appropriately.

This is all nice talk, but I don't think I'll have the time or courage to do any of this so… thanks for the great package anyway! ☺

[nikohansen]

FTR (note to self), cma.utilities.utils.print_warning is used to print warnings. Hence only this function would need to be changed to become compliant in the warning case. EDIT: and the doctests need to be fixed.

[nikohansen]

Some bookkeeping:

• evolution_strategy prints the say hello message and in results_pretty
• logger prints in some places where it should warn and while plotting
• print_warning calls warnings.warn