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annotate roundup/backends/__init__.py @ 2978:4fcb61bfe4ec

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clean up comment
author Anthony Baxter <anthonybaxter@users.sourceforge.net>
date Mon, 29 Nov 2004 07:34:39 +0000
parents e03ef8a8df7f
children b286373a517f
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1 #
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2 # Copyright (c) 2001 Bizar Software Pty Ltd (http://www.bizarsoftware.com.au/)
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3 # This module is free software, and you may redistribute it and/or modify
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4 # under the same terms as Python, so long as this copyright message and
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5 # disclaimer are retained in their original form.
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6 #
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7 # IN NO EVENT SHALL BIZAR SOFTWARE PTY LTD BE LIABLE TO ANY PARTY FOR
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8 # DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING
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9 # OUT OF THE USE OF THIS CODE, EVEN IF THE AUTHOR HAS BEEN ADVISED OF THE
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10 # POSSIBILITY OF SUCH DAMAGE.
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11 #
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12 # BIZAR SOFTWARE PTY LTD SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
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13 # BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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14 # FOR A PARTICULAR PURPOSE. THE CODE PROVIDED HEREUNDER IS ON AN "AS IS"
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15 # BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE,
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16 # SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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17 #
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18 # $Id: __init__.py,v 1.33 2004-11-29 07:34:39 anthonybaxter Exp $
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19
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20 '''Container for the hyperdb storage backend implementations.
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21 '''
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22 __docformat__ = 'restructuredtext'
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23
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24 import sys
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25
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26 # These names are used to suppress import errors.
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27 # If get_backend raises an ImportError with appropriate
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28 # module name, have_backend quietly returns False.
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29 # Otherwise the error is reraised.
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30 _modules = {
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31 'mysql': 'MySQLdb',
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32 'postgresql': 'psycopg',
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33 }
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34
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35 def get_backend(name):
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36 '''Get a specific backend by name.'''
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37 vars = globals()
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38 # if requested backend has been imported yet, return current instance
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39 if vars.has_key(name):
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40 return vars[name]
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41 # import the backend module
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42 module_name = 'back_%s' % name
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43 try:
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44 module = __import__(module_name, vars)
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45 except:
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46 # import failed, but in versions prior to 2.4, a (broken)
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47 # module is left in sys.modules and package globals;
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48 # subsequent imports would succeed and get the broken module.
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49 # This no longer happens in Python 2.4 and later.
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50 if sys.version_info < (2, 4):
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51 del sys.modules['.'.join((__name__, module_name))]
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52 del vars[module_name]
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53 raise
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54 else:
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55 vars[name] = module
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56 return module
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57
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58 def have_backend(name):
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59 '''Is backend "name" available?'''
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60 try:
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61 get_backend(name)
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62 return 1
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63 except ImportError, e:
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64 global _modules
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65 if not str(e).startswith('No module named %s'
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66 % _modules.get(name, name)):
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67 raise
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68 return 0
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69
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70 def list_backends():
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71 '''List all available backend names.
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72
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73 This function has side-effect of registering backward-compatible
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74 globals for all available backends.
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75
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76 '''
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77 l = []
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78 for name in 'anydbm', 'mysql', 'sqlite', 'metakit', 'postgresql':
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79 if have_backend(name):
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80 l.append(name)
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81 return l
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82
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83 # vim: set filetype=python sts=4 sw=4 et si :
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