Saying "of course"
 

Hi,

Are these interchangeable?

como no (of course, why not?)
por supuesto que sí (of course, yes)

Pimsleur had been using "como no" for a while to say "of course". Now they switched to "por supuesto que sí" to mean the same thing "of course". No explanation as to why we're using the latter now.

Is it safe to use either? Do they mean the same?

Thanks,
Jon Hayden

'Como no' means 'why not'. It means you're saying 'yes' to whatever you heard or were asked to do.
'Claro que sí' and 'por supuesto que sí' mean both 'yes' and 'of course' basically at the same time. You are responding favorably to a request or an idea.
These are just three ways to show agreement. There are more.

The first means 'yes,' but it sometimes implies that you had to talk yourself into it. So if that is your reason for using it, then the two are not interchangeable.

I agree with Rusty.
In Mexico "Cómo no", as a reply to a request, it means you will be happy to do what you're being asked to do. Just like the other two, you may not really mean it, but the context will tell. :D

Haha. Thanks to both of you. So Como No sounds like a begrudging yes. And por supuesto que si, sounds like you're happy to do it.

It's not necessarily begrudging. I can be quite affirmative. As Angelica states,
it all depends on tone and context.

Yeah, I guess you could make anything sound nice with how you say it :)