# 7.7 Standard Module `whichdb`

The single function in this module attempts to guess which of the several simple database modules available-dbm, gdbm, or dbhash-should be used to open a given file.

`whichdb` (filename)
  Returns one of the following values: `None` if the file can't be opened because it's unreadable or doesn't exist; the empty string (`""`) if the file's format can't be guessed; or a string containing the required module name, such as `"dbm"` or `"gdbm"`.