Acing the technical interview in Python

class nil:
  pass

def cons(x, y):
  return lambda v: x if v else y

def nth(l, n):
  if l is nil:
    return None
  elif n == 0:
    return l(True)
  else:
    return nth(l(False), n-1)

def prn_list(l):
  print("("),
  def inner(l):
    if l is nil:
      print(")")
    else:
      print(l(True)),
      if l(False) is not nil:
        print(" "),
      inner(l(False))
  inner(l)

def reverse(l):
  def inner(r, l):
    if l is not nil:
      return inner(cons(l(True),r),l(False))
    else:
      return r
  return inner(nil,l)

if __name__ == "__main__":
  l = cons(1,cons(2,cons(3,nil)))
  prn_list(l)
  prn_list(reverse(l))