2363d6de43
git-svn-id: http://google-refine.googlecode.com/svn/trunk@517 7d457c2a-affb-35e4-300a-418c747d4874
84 lines
2.6 KiB
Python
84 lines
2.6 KiB
Python
"""Generic interface to all dbm clones.
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Instead of
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import dbm
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d = dbm.open(file, 'w', 0666)
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use
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import anydbm
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d = anydbm.open(file, 'w')
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The returned object is a dbhash, gdbm, dbm or dumbdbm object,
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dependent on the type of database being opened (determined by whichdb
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module) in the case of an existing dbm. If the dbm does not exist and
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the create or new flag ('c' or 'n') was specified, the dbm type will
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be determined by the availability of the modules (tested in the above
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order).
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It has the following interface (key and data are strings):
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d[key] = data # store data at key (may override data at
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# existing key)
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data = d[key] # retrieve data at key (raise KeyError if no
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# such key)
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del d[key] # delete data stored at key (raises KeyError
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# if no such key)
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flag = key in d # true if the key exists
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list = d.keys() # return a list of all existing keys (slow!)
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Future versions may change the order in which implementations are
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tested for existence, add interfaces to other dbm-like
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implementations.
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The open function has an optional second argument. This can be 'r',
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for read-only access, 'w', for read-write access of an existing
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database, 'c' for read-write access to a new or existing database, and
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'n' for read-write access to a new database. The default is 'r'.
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Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it
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only if it doesn't exist; and 'n' always creates a new database.
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"""
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class error(Exception):
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pass
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_names = ['dbhash', 'gdbm', 'dbm', 'dumbdbm']
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_errors = [error]
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_defaultmod = None
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for _name in _names:
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try:
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_mod = __import__(_name)
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except ImportError:
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continue
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if not _defaultmod:
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_defaultmod = _mod
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_errors.append(_mod.error)
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if not _defaultmod:
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raise ImportError, "no dbm clone found; tried %s" % _names
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error = tuple(_errors)
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def open(file, flag = 'r', mode = 0666):
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# guess the type of an existing database
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from whichdb import whichdb
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result=whichdb(file)
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if result is None:
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# db doesn't exist
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if 'c' in flag or 'n' in flag:
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# file doesn't exist and the new
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# flag was used so use default type
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mod = _defaultmod
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else:
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raise error, "need 'c' or 'n' flag to open new db"
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elif result == "":
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# db type cannot be determined
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raise error, "db type could not be determined"
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else:
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mod = __import__(result)
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return mod.open(file, flag, mode)
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