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)
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