The problem is that the repr of the underlying db is not very helpful either, as seen for the dbm backend.

>>> import dbm
>>> dbm.open("test", "c")
<dbm.dumb._Database object at 0x03091FC0>
>>> f=_
>>> f[b"2"] = b"a"
>>> f
<dbm.dumb._Database object at 0x03091FC0>
>>>

But it shows the content of the underlying database, not the key / value pairs passed in the constructor:

>>> shelve.open("test1")
DbfilenameShelf({})
>>> f=_
>>> f["2"] = "4"
>>> f
DbfilenameShelf({'2': '4'})
>>> f["40"] = "50"
>>> f.dict
<dbm.dumb._Database object at 0x02ACC038>
>>> f.dict.keys()
[b'40', b'2']
>>>