old_contents: # sum of even fibonacci numbers below 4 million? 
  
  import timeit
  
  
  start = timeit.default_timer()
  
  #def euler_2():
  #    a1 = 1
  #    b1 = 1
  #    b2 = 0
  #    limit = 4000000
  #    while b2 <= limit:
  #        b2 = a1 + b1
  #        a1 = b1
  #        b1 = b2
  #        if b2 % 2 == 0:
  #            yield b2
  
  def euler_2(t=0, n=2, ln=1):
      if n >= 4000000:
          return t 
      if n % 2 == 0:
          return euler_2(t + n, n + ln, n)
      return euler_2(t, n + ln, n)
  
  print "Answer: %s" % euler_2() 
  #print "Answer: %s" % sum([i for i in euler_2()])
  stop = timeit.default_timer()
  print "Time: %f" % (stop - start)
  
new_contents: # sum of even fibonacci numbers below 4 million? 
  
  import timeit
  
  
  start = timeit.default_timer()
  
  #def euler_2():
  #    a1 = 1
  #    b1 = 1
  #    b2 = 0
  #    limit = 4000000
  #    while b2 <= limit:
  #        b2 = a1 + b1
  #        a1 = b1
  #        b1 = b2
  #        if b2 % 2 == 0:
  #            yield b2
  
  def euler_2(t=0, n=2, ln=1):
      if n >= 4000000: return t
      elif n % 2 == 0: return euler_2(t + n, n + ln, n)
      return euler_2(t, n + ln, n)
  
  print "Answer: %s" % euler_2() 
  #print "Answer: %s" % sum([i for i in euler_2()])
  stop = timeit.default_timer()
  print "Time: %f" % (stop - start)
  
subject: return on same line