> less than? i doubt that... if you import the module it's one lookup more (at least in theory)

``` python
import timeit
def test():
    from datetime import timedelta
    timedelta(microseconds=-1)

def test1():
    import datetime
    datetime.timedelta(microseconds=-1)

timeit.timeit(test, number=10000000)
> 17.780892848968506
timeit.timeit(test1, number=10000000)
> 13.522549152374268
```
~24%, that may be important only when we use ```import``` in very heavy loops, so, in practice, difference in cost is negligibly.