how can i merge keys and values in a dictionary?

It’s telling you what’s wrong: you can’t change the size of total_personality_count_dict while iterating through it. You can’t use pop(). Since you are doing addition, what you can do instead is update the value of the field you want to “remove” to 0, so any future addition done with it will not have any effect.

total_personality_count_dict[personality_2] = 0

And if you want a dictionary without personality_2, create a new dictionary and store the updates you want to keep there instead.