This idea results from issue of user files shadowing stdlib files on import. There was a thread on pydev about this yesterday. There is also an opposite issue of builtin modules shadowing user files. The keyword module provides kwlist and iskeyword function. One use of kwlist is used in some other stdlib modules and can be used by syntax highlighters (as in IDLE). Kwlist is updated by the main function. A module module would have at least liblist and islibmodule function. Liblist would contain all directories with __init__.py and all .py files. (I don't think files within package directories should be included, as there is no direct shadowing problem.) A python oriented editor could then warn on save requests "This name matches a stdlib name in /Lib. If you run python in this directory, you will not be able to import the stdlib module. Continue?". The module should also have binlist and isbinmodule for builtin modules. (I do not know how to get such a list. If necessary, an api could be added.) An editor could than warn "This name matches a builtin stdlib name. You will not be able to import this file. Continue?". -- Terry Jan Reedy