I don't think "you can define + on custom data types" to be the same as implicit behavior. "Explicit is better than implicit" is more around things like Django

I don't think "you can define + on custom data types" to be the same as implicit behavior. "Explicit is better than implicit" is more around things like Django not just automatically importing every directory it sees (instead requiring you to list the apps used). It's also a decent rationale for changes made from Py2 to Py3 regarding bytes-to-string conversions needing to happen explicitly. It's also about how usually you end up explicitly listing imports (wildcard imports exist but are pretty sparing), or lacking implicit type conversions between data types. This stuff is of course dependent on what library you are using, the projects you are working on, etc. And there's a certain level of mastery expected. But I think the general ideas exist despite the language allowing for much more in theory.