Mercurial > cpython-lru_cache-weakref

annotate Lib/anydbm.py @ 54294:dba767bc3155 legacy-trunk

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remove mention of old ctypes version
author Benjamin Peterson <benjamin@python.org>
date Sat, 23 May 2009 20:59:09 +0000
parents a1de0bab5475
children 229c28cb9afb 5c3f3d352e0a
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1 """Generic interface to all dbm clones.
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2
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3 Instead of
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4
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5 import dbm
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6 d = dbm.open(file, 'w', 0666)
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7
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8 use
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9
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10 import anydbm
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11 d = anydbm.open(file, 'w')
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12
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13 The returned object is a dbhash, gdbm, dbm or dumbdbm object,
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14 dependent on the type of database being opened (determined by whichdb
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15 module) in the case of an existing dbm. If the dbm does not exist and
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16 the create or new flag ('c' or 'n') was specified, the dbm type will
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17 be determined by the availability of the modules (tested in the above
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18 order).
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19
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20 It has the following interface (key and data are strings):
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21
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22 d[key] = data # store data at key (may override data at
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23 # existing key)
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24 data = d[key] # retrieve data at key (raise KeyError if no
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25 # such key)
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26 del d[key] # delete data stored at key (raises KeyError
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27 # if no such key)
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28 flag = key in d # true if the key exists
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29 list = d.keys() # return a list of all existing keys (slow!)
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30
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31 Future versions may change the order in which implementations are
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32 tested for existence, add interfaces to other dbm-like
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33 implementations.
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34
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35 The open function has an optional second argument. This can be 'r',
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36 for read-only access, 'w', for read-write access of an existing
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37 database, 'c' for read-write access to a new or existing database, and
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38 'n' for read-write access to a new database. The default is 'r'.
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39
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40 Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it
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41 only if it doesn't exist; and 'n' always creates a new database.
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42
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43 """
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44
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45 class error(Exception):
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46 pass
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47
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48 _names = ['dbhash', 'gdbm', 'dbm', 'dumbdbm']
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49 _errors = [error]
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50 _defaultmod = None
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51
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52 for _name in _names:
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53 try:
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54 _mod = __import__(_name)
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55 except ImportError:
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56 continue
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57 if not _defaultmod:
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58 _defaultmod = _mod
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59 _errors.append(_mod.error)
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60
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61 if not _defaultmod:
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62 raise ImportError, "no dbm clone found; tried %s" % _names
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63
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64 error = tuple(_errors)
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65
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66 def open(file, flag = 'r', mode = 0666):
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67 # guess the type of an existing database
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68 from whichdb import whichdb
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69 result=whichdb(file)
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70 if result is None:
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71 # db doesn't exist
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72 if 'c' in flag or 'n' in flag:
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73 # file doesn't exist and the new
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74 # flag was used so use default type
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75 mod = _defaultmod
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76 else:
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77 raise error, "need 'c' or 'n' flag to open new db"
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78 elif result == "":
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79 # db type cannot be determined
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80 raise error, "db type could not be determined"
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81 else:
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82 mod = __import__(result)
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83 return mod.open(file, flag, mode)