Ошибка модуля shelve: db type could not be determined

import shelve
 
a = shelve.open('data.db')

C:\Python\test>python py.py
Traceback (most recent call last):
  File "py.py", line 22, in <module>
    a = shelve.open(os.path.join(curdir, 'data.db'))
  File "C:\Python\lib\shelve.py", line 239, in open
    return DbfilenameShelf(filename, flag, protocol, writeback)
  File "C:\Python\lib\shelve.py", line 223, in __init__
    Shelf.__init__(self, dbm.open(filename, flag), protocol, writeback)
  File "C:\Python\lib\dbm\__init__.py", line 88, in open
    raise error[0]("db type could not be determined")
dbm.error: db type could not be determined
 
C:\Python\test>

C:\Python\test>python py.py
Traceback (most recent call last):
  File "py.py", line 21, in <module>
    a = shelve.open('data.db')
  File "C:\Python\lib\shelve.py", line 239, in open
    return DbfilenameShelf(filename, flag, protocol, writeback)
  File "C:\Python\lib\shelve.py", line 223, in __init__
    Shelf.__init__(self, dbm.open(filename, flag), protocol, writeback)
  File "C:\Python\lib\dbm\__init__.py", line 88, in open
    raise error[0]("db type could not be determined")
dbm.error: db type could not be determined
 
C:\Python\test>

import shelve
 
test = {'a': 1, 'b': 2}
 
bd = shelve.open('data.db')
bd['test'] = test
bd.close()

import shelve
 
bd = shelve.open('data.db')
print(bd['test'])
bd.close()

import shelve
 
test = {'a': 1, 'b': 2}
 
bd = shelve.open("data.db")
bd['test'] = test
bd.close()

Traceback (most recent call last):
  File "os.py", line 8, in <module>
    bd = shelve.open("data.db")
  File "/usr/lib/python3.4/shelve.py", line 239, in open
    return DbfilenameShelf(filename, flag, protocol, writeback)
  File "/usr/lib/python3.4/shelve.py", line 223, in __init__
    Shelf.__init__(self, dbm.open(filename, flag), protocol, writeback)
  File "/usr/lib/python3.4/dbm/__init__.py", line 88, in open
    raise error[0]("db type could not be determined")
dbm.error: db type could not be determined