Setuptools comes to around 100kloc now (per a naive search and `wc` of the .py files in a new environment) and installs without a hitch for everyone. Pip, nearly double that. Yes, both of those are heavily using vendoring, but because of bootstrapping problems because they are the default build tool and package installer respectively. (And quite a bit of devendoring would be possible if some system maintainers didn't insist on "building from source" when there is only Python code. Yes, technically pre-compiling .py to .pyc can be considered "building", but pip would already do that during installation.) If they didn't have to worry about those issues (or the additional Pip issue of "how do you get the packages for Pip's dependencies if you don't already have Pip?"), they would install and run just fine from a series of wheels that are all pure Python code.

For that matter, one of those dependencies, `pyparsing`, is around 10k lines installed (and the repository is much larger with tests etc.). That's with it not having any dependencies of its own.

There is no real barrier anywhere around the 1k loc mark. The problems large projects run into have more subtle causes.