Unless you want to put steel edging around it you will have to contain it manually. Never planted it in containers but don't see a problem with it along as it doesn't get full sun and it's in compost. If you amend the soil where planting it in the shade it should have no problem spreading.

Here is a link that might be useful: Propagating Perennials

I'll try it in a large planter. Thanks.
Do you think the sun would contain it? I will plant in shade of course, but in the ground, would I have to worry about it spreading to areas of full sun? What I'm hoping is that the shade would contain it- that it won't leave the shade, really.

It depends. If it got enough moisture along with a good soil base the sun may not contain its spread. Make a mental note to check its growtrh in the fall.

Here is a link that might be useful: Propagating Perennials