is there a pythonic way for doing that ?

As someone mentioned before, you should treat your pulumi code as the declarative way of getting your resources deployed. So in this case, is better that you just import the resource into pulumi (pulumi import) and manage it from there. If you still want to check the existence of a resource instead then use any of the helper functions (getResource(), lookupResource()).

As a follow up here, as indicated you should always have the desired state of Pulumi. At a minimum, ensure the resource is imported and managed into the state. As a workaround, if another program/process/etc is responsible for changing some properties of the resource and you are just trying to avoid Pulumi from "fighting" with it, you could leverage the IgnoreChanges feature to exclude certain properties that the other process "owns": https://www.pulumi.com/docs/intro/concepts/resources/options/ignorechanges/ I don't think it should be overused. At a certain point, depending on what the resource is, it should be decided who or what is an authoritative owner of something when you get right down to it...