R. David Murray added the comment:
This has always been the case (that gdbm and ndbm are not supported on
windows). See also issue 3769 for background and dbm and windows, and issue
3783 for something to work on if you want to contribute to making the dbm story
on windows better.
Googling
New submission from Arthur Vanwalleghen:
When I tried to work with GDBM and Ndbm files I saw that their supporting
modules were not found. This can be verified with Pydoc:
Pydoc\Python36-32\lib \dbm(package)\Package Contents\gnu|ndbm
ErrorDuringImport: problem in dbm.gnu -
