Thanks for this great tutorial. It really helped me understand the A* method. I know this post is now more than a year old, but I followed it now and noticed something that maybe I do not understand right or might be interesting for others to know:

In the process function on line 17, I think that ‘if c in self.op:’ can never be true since self.op is actually a list of tuples, not a list of cell objects. This leads to the same cell being added multiple times to the open list and eventually slows the algorithm down or even creates an infinity loop in some situations. Am I missing something here or is this really a bug?

Maybe grid numbers next to the images would help when looking up coordinates repeatedly? Otherwise keep up the python articles!