Are dummies a real good thing to train with when you don't have a partner to train with? How do they compare to an actual partner? Can you get a real good training session with one of these?

I am asking this because most of the time during the summer I'm out of town and I can't train with my partners so I was looking into these and wandering if they are good enough to replace an actual human for up to 2-3 months of training.