User Input Validation in Jython

Question

I have been attempting a mirroring assignment using Jython Environment for students.

I am seeking to request an arbitrary line from the user which I will use to mirror the image, this line has to be from an image edge to an edge and be a diagonal.

def userCoordinates():
  pic = makePicture(pickAFile())
  height = getHeight(pic)
  width = getWidth(pic)
  newPic = makeEmptyPicture, (width, height)

startX = requestInteger("Please enter your startX Coordinate")
while startX > width:
  startX = requestInteger("Error, this coordinate is outside the image, please enter your startX Coordinate") 
else:
  print "Your startX coordinate is", startX

startY =  requestInteger("Please enter your startY Coordinate")
while startY > height:
  startY = requestInteger("Error, this coordinate is outside the image, please enter your startY Coordinate")
else:
  print "Your startY coordinate is", startY

endX =  requestInteger("Please enter your endX Coordinate")
while endX > width:
  endX = requestInteger("Error, this coordinate is outside the image, please enter your endX Coordinate")
else:
  print "Your endX coordinate is", endX

endY =  requestInteger("Please enter your endY Coordinate")
while endY > height:
  endY = requestInteger("Error, this coordinate is outside the image, please enter your endY Coordinate")
else:
  print "Your endY coordinate is", endY

Is there any way to validate that the point selected is on the edges of the image? Or a better(cleaner way) to do above. Im a beginner in all ways.

I tried using while startX != 0 or startX != width

but then this will not work as the X really could be anything

Any help would be greatly appreciated!