[pygame] Rect collision by direction

[Skizzaltix <waterflight@xxxxxxxxxxxxx>]

Hello,
I've been trying to find a way to, when detecting collisions between two 
sprites, determine which side of one sprite is colliding with the other. 
Basically, I want to make it so that when a character walking to the 
left collides with a block to his/her left, he/she stops moving, but if 
the character is moving slightly downwards, he/she will continue moving 
down, but stop moving to the left.
I'm sure there's some simple solution to this, which I have been missing 
entirely.
Thanks!
--Skizzaltix