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86530b38 AT |
1 | """Generic interface to all dbm clones. |
2 | ||
3 | Instead of | |
4 | ||
5 | import dbm | |
6 | d = dbm.open(file, 'w', 0666) | |
7 | ||
8 | use | |
9 | ||
10 | import anydbm | |
11 | d = anydbm.open(file, 'w') | |
12 | ||
13 | The returned object is a dbhash, gdbm, dbm or dumbdbm object, | |
14 | dependent on the type of database being opened (determined by whichdb | |
15 | module) in the case of an existing dbm. If the dbm does not exist and | |
16 | the create or new flag ('c' or 'n') was specified, the dbm type will | |
17 | be determined by the availability of the modules (tested in the above | |
18 | order). | |
19 | ||
20 | It has the following interface (key and data are strings): | |
21 | ||
22 | d[key] = data # store data at key (may override data at | |
23 | # existing key) | |
24 | data = d[key] # retrieve data at key (raise KeyError if no | |
25 | # such key) | |
26 | del d[key] # delete data stored at key (raises KeyError | |
27 | # if no such key) | |
28 | flag = key in d # true if the key exists | |
29 | list = d.keys() # return a list of all existing keys (slow!) | |
30 | ||
31 | Future versions may change the order in which implementations are | |
32 | tested for existence, add interfaces to other dbm-like | |
33 | implementations. | |
34 | ||
35 | The open function has an optional second argument. This can be 'r', | |
36 | for read-only access, 'w', for read-write access of an existing | |
37 | database, 'c' for read-write access to a new or existing database, and | |
38 | 'n' for read-write access to a new database. The default is 'r'. | |
39 | ||
40 | Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it | |
41 | only if it doesn't exist; and 'n' always creates a new database. | |
42 | ||
43 | """ | |
44 | ||
45 | class error(Exception): | |
46 | pass | |
47 | ||
48 | _names = ['dbhash', 'gdbm', 'dbm', 'dumbdbm'] | |
49 | _errors = [error] | |
50 | _defaultmod = None | |
51 | ||
52 | for _name in _names: | |
53 | try: | |
54 | _mod = __import__(_name) | |
55 | except ImportError: | |
56 | continue | |
57 | if not _defaultmod: | |
58 | _defaultmod = _mod | |
59 | _errors.append(_mod.error) | |
60 | ||
61 | if not _defaultmod: | |
62 | raise ImportError, "no dbm clone found; tried %s" % _names | |
63 | ||
64 | error = tuple(_errors) | |
65 | ||
66 | def open(file, flag = 'r', mode = 0666): | |
67 | # guess the type of an existing database | |
68 | from whichdb import whichdb | |
69 | result=whichdb(file) | |
70 | if result is None: | |
71 | # db doesn't exist | |
72 | if 'c' in flag or 'n' in flag: | |
73 | # file doesn't exist and the new | |
74 | # flag was used so use default type | |
75 | mod = _defaultmod | |
76 | else: | |
77 | raise error, "need 'c' or 'n' flag to open new db" | |
78 | elif result == "": | |
79 | # db type cannot be determined | |
80 | raise error, "db type could not be determined" | |
81 | else: | |
82 | mod = __import__(result) | |
83 | return mod.open(file, flag, mode) |