>>> my_list = [345.787,786.7545,9.9887,243.89]
>>> for i in my_list:
... w = 3.9 * i **2
... print("Value: %10.2f %11.3f" % (w, w))
...
Value: 466317.73 466317.733
Value: 2414032.31 2414032.309
Value: 389.12 389.119
Value: 231981.10 231981.095
>>>
>>>
>>> for i in my_list:
... print("Value: {0:10.2f} {0:11.3f}".format(3.9 * i **2))
...
Value: 466317.73 466317.733
Value: 2414032.31 2414032.309
Value: 389.12 389.119
Value: 231981.10 231981.095
>>>