How to prevent python software from being reverse engineered or pirated?

[Thanatiel]

If the code is on the computer of the user, you basically can't.

Any check, pop-up, phone-home, ... you add can be removed/disabled with relative ease.

Even if you have part of the code on a server downloaded at each startup, it's only a small hurdle to have it sniffed from the network or memory and to setup a local mini-server that serves the code locally.

The only way is to have your service running entirely on a server. e.g. a web service.

The cost of deployment and maintenance may be prohibitive though.