It's readable

def equalStacks(h1, h2, h3): h1.reverse() h2.reverse() h3.reverse()

stacks = [h1, h2, h3]

heights = [sum(stack) for stack in stacks]
while True:
    if len(set(heights)) == 1:
        return heights[0]
    else:
        idx = heights.index(max(heights))
        heights[idx] -= stacks[idx].pop()