Comment 2 for bug 1598810

(srly, bugreports referring to pastebin?)

Well, apts output says what is going on: As a package with that name doesn't exist and the string looks like a regex (thanks to the '.') it will search for packages matching the regex and it does find one. That is perfectly fine and established behavior which is impossible to change without breaking existing users.

Note that the package python3.4 doesn't exist at all in the view of apt, which triggers this. If ANY package would give it as much as a passing hint that it ever existed (by having any sort of dependency on it) apt would actually error out in a way you would like it to (saying that python3.4 isn't available for install, but is referenced by other packages – pointing to the potential of being replaced by something else or distributed in another repository). That is also perfectly fine and established behavior which is impossible to change by now.

Anyway, a workaround for your setup might be using '^python3\.4$'.

So, as there is no bug to be found, closing as opinion. We could treat it as a wish for controlling how the string is interpreted, but that will actually be a tiny by-product of patterns – and is in no way helping apt versions without patterns as a feature, which is the subtext of this bugreport.

P.S.: The automation to make stuff available for an application is called packaging, not running apt commands automatically as this has failure modes like this, makes changes so much harder for the python side as well as the application side, destroys automatic removal and and and which is why package management was invented decades ago in the first place.