old_contents: 
  class PPU():
      def __init__(self, cpu):
          self.cpu = cpu
  
          self.ctrl       = 0x2000
          self.mask       = 0x2001
          self.status     = 0x2002
          self.oamaddr    = 0x2003
          self.scroll     = 0x2005
          self.addr       = 0x2006
          self.data       = 0x2007
  
      def stepPPU(self):
          # each step draws one pixel
          pass
  
      def runPPU(self, numCPUCycles):
          # we get to run 3 PPU cycles for every 1 CPU cycle
          # we step the CPU first, then based on how long the 
          # instruction took, we step the PPU 3x that number
          for i in range(0, numCPUCycles*3):
              self.stepPPU()
  
new_contents: 
  class PPU():
      def __init__(self, cpu):
          self.cpu = cpu
  
          self.ctrl       = 0x2000
          self.mask       = 0x2001
          self.status     = 0x2002
          self.oamaddr    = 0x2003
          self.oamdata    = 0x2004
          self.scroll     = 0x2005
          self.addr       = 0x2006
          self.data       = 0x2007
  
      def stepPPU(self):
          # each step draws one pixel
          pass
  
      def runPPU(self, numCPUCycles):
          # we get to run 3 PPU cycles for every 1 CPU cycle
          # we step the CPU first, then based on how long the 
          # instruction took, we step the PPU 3x that number
          for i in range(0, numCPUCycles*3):
              self.stepPPU()
  
subject: Add oamdata addr