Stack sort

def sort(stack):
  if len(stack) == 1:
    return stack
  mid = len(stack)//2
  oStack = []
  for i in range(mid): # move top half to other stack
    oStack.append(stack.pop())
  sort(oStack)
  sort(stack)

  fStack = [] # Merge into final stack
  while len(stack) > 0 and len(oStack) > 0:
    if stack[-1] < oStack[-1]:
      fStack.append(stack.pop())
    else:
      fStack.append(oStack.pop())

  while len(stack) > 0:
    fStack.append(stack.pop())

  while len(oStack) > 0:
    fStack.append(oStack.pop())

  while len(fStack) > 0: # Move everything from final stack to stack as it is in reverse on final stack
    stack.append(fStack.pop())
  return stack

print(sort([1,2,5,1,3,7,8,1,2,10,12,7]))