build/lib/roundup/backends/__init__.py

   1 #
   2 # Copyright (c) 2001 Bizar Software Pty Ltd (http://www.bizarsoftware.com.au/)
   3 # This module is free software, and you may redistribute it and/or modify
   4 # under the same terms as Python, so long as this copyright message and
   5 # disclaimer are retained in their original form.
   6 #
   7 # IN NO EVENT SHALL BIZAR SOFTWARE PTY LTD BE LIABLE TO ANY PARTY FOR
   8 # DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING
   9 # OUT OF THE USE OF THIS CODE, EVEN IF THE AUTHOR HAS BEEN ADVISED OF THE
  10 # POSSIBILITY OF SUCH DAMAGE.
  11 #
  12 # BIZAR SOFTWARE PTY LTD SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  13 # BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  14 # FOR A PARTICULAR PURPOSE.  THE CODE PROVIDED HEREUNDER IS ON AN "AS IS"
  15 # BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE,
  16 # SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  17 #
  18 # $Id: __init__.py,v 1.40 2007-11-07 20:47:12 richard Exp $
  19
  20 '''Container for the hyperdb storage backend implementations.
  21 '''
  22 __docformat__ = 'restructuredtext'
  23
  24 import sys
  25
  26 # These names are used to suppress import errors.
  27 # If get_backend raises an ImportError with appropriate
  28 # module name, have_backend quietly returns False.
  29 # Otherwise the error is reraised.
  30 _modules = {
  31     'mysql': ('MySQLdb',),
  32     'postgresql': ('psycopg',),
  33     'tsearch2': ('psycopg',),
  34     'sqlite': ('pysqlite', 'pysqlite2', 'sqlite3', '_sqlite3', 'sqlite'),
  35 }
  36
  37 def get_backend(name):
  38     '''Get a specific backend by name.'''
  39     vars = globals()
  40     # if requested backend has been imported yet, return current instance
  41     if name in vars:
  42         return vars[name]
  43     # import the backend module
  44     module_name = 'back_%s' % name
  45     try:
  46         module = __import__(module_name, vars)
  47     except:
  48         # import failed, but in versions prior to 2.4, a (broken)
  49         # module is left in sys.modules and package globals;
  50         # subsequent imports would succeed and get the broken module.
  51         # This no longer happens in Python 2.4 and later.
  52         if sys.version_info < (2, 4):
  53             del sys.modules['.'.join((__name__, module_name))]
  54             del vars[module_name]
  55         raise
  56     else:
  57         vars[name] = module
  58         return module
  59
  60 def have_backend(name):
  61     '''Is backend "name" available?'''
  62     if name == 'tsearch2':
  63         # currently not working
  64         return 0
  65     try:
  66         get_backend(name)
  67         return 1
  68     except ImportError, e:
  69         for name in _modules.get(name, (name,)):
  70             if str(e).startswith('No module named %s'%name):
  71                 return 0
  72         raise
  73     return 0
  74
  75 def list_backends():
  76     '''List all available backend names.
  77
  78     This function has side-effect of registering backward-compatible
  79     globals for all available backends.
  80
  81     '''
  82     l = []
  83     for name in 'anydbm', 'mysql', 'sqlite', 'postgresql':
  84         if have_backend(name):
  85             l.append(name)
  86     return l
  87
  88 # vim: set filetype=python sts=4 sw=4 et si :