[carreau]

There is the %autoreload magic but it is limited, it will often fail to reload compiled modules like numpy. So there is not a single answer, sometime it works, other times it does not.

[bulibuta]

Exactly! So I end up always restarting to be sure that I don't waste time chasing already-fixed-bugs.

[carreau]

May I suggest to look at https://eradman.com/entrproject/ ? It's like watch but triggers only when it detect file changes.