"""Generic interface to all dbm clones. | |
Instead of | |
import dbm | |
d = dbm.open(file, 'w', 0666) | |
use | |
import anydbm | |
d = anydbm.open(file, 'w') | |
The returned object is a dbhash, gdbm, dbm or dumbdbm object, | |
dependent on the type of database being opened (determined by whichdb | |
module) in the case of an existing dbm. If the dbm does not exist and | |
the create or new flag ('c' or 'n') was specified, the dbm type will | |
be determined by the availability of the modules (tested in the above | |
order). | |
It has the following interface (key and data are strings): | |
d[key] = data # store data at key (may override data at | |
# existing key) | |
data = d[key] # retrieve data at key (raise KeyError if no | |
# such key) | |
del d[key] # delete data stored at key (raises KeyError | |
# if no such key) | |
flag = key in d # true if the key exists | |
list = d.keys() # return a list of all existing keys (slow!) | |
Future versions may change the order in which implementations are | |
tested for existence, and add interfaces to other dbm-like | |
implementations. | |
""" | |
class error(Exception): | |
pass | |
_names = ['dbhash', 'gdbm', 'dbm', 'dumbdbm'] | |
_errors = [error] | |
_defaultmod = None | |
for _name in _names: | |
try: | |
_mod = __import__(_name) | |
except ImportError: | |
continue | |
if not _defaultmod: | |
_defaultmod = _mod | |
_errors.append(_mod.error) | |
if not _defaultmod: | |
raise ImportError, "no dbm clone found; tried %s" % _names | |
error = tuple(_errors) | |
def open(file, flag='r', mode=0666): | |
"""Open or create database at path given by *file*. | |
Optional argument *flag* can be 'r' (default) for read-only access, 'w' | |
for read-write access of an existing database, 'c' for read-write access | |
to a new or existing database, and 'n' for read-write access to a new | |
database. | |
Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it | |
only if it doesn't exist; and 'n' always creates a new database. | |
""" | |
# guess the type of an existing database | |
from whichdb import whichdb | |
result=whichdb(file) | |
if result is None: | |
# db doesn't exist | |
if 'c' in flag or 'n' in flag: | |
# file doesn't exist and the new | |
# flag was used so use default type | |
mod = _defaultmod | |
else: | |
raise error, "need 'c' or 'n' flag to open new db" | |
elif result == "": | |
# db type cannot be determined | |
raise error, "db type could not be determined" | |
else: | |
mod = __import__(result) | |
return mod.open(file, flag, mode) |