How to limit time precision to milliseconds in python?

Question

Python

There is a variable in python
result = datetime.datetime.now()
How to limit the accuracy to milliseconds (accuracy to microseconds by default)
Tried to do something like

result.microsecond = int(result.microsecond / 1000) * 1000

But the python swears:

AttributeError: attribute 'microsecond' of 'datetime.datetime' objects is not writable