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# Copyright (C) 2006-2010 Canonical Ltd
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# Copyright (C) 2006, 2008 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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"""Classes to provide name-to-object registry-like support."""
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from .pyutils import get_named_object
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class _ObjectGetter(object):
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"""Maintain a reference to an object, and return the object on request.
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return the imported object.
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if not self._imported:
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self._obj = get_named_object(self._module_name, self._member_name)
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return super(_LazyObjectGetter, self).get_obj()
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segments = self._member_name.split('.')
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names = [self._member_name]
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obj = __import__(self._module_name, globals(), locals(), names)
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for segment in segments:
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obj = getattr(obj, segment)
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def __repr__(self):
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return "<%s.%s object at %x, module=%r attribute=%r imported=%r>" % (
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return "<%s.%s object at %x, module=%r attribute=%r>" % (
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self.__class__.__module__, self.__class__.__name__, id(self),
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self._module_name, self._member_name, self._imported)
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self._module_name, self._member_name)
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class Registry(object):
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self._default_key = None
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# Map from key => (is_lazy, info)
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self._help_dict = {}
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self._info_dict = {}
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"""Return a set of the format names which are aliases."""
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return dict(self._aliases.items())
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for alias, target in self._aliases.items():
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ret.setdefault(target, []).append(alias)
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def register(self, key, obj, help=None, info=None,
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override_existing=False):
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"""Register a new object to a name.
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override_existing=False):
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"""Register a new object to be loaded on request.
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:param key: This is the key to use to request the object later.
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:param module_name: The python path to the module. Such as 'os.path'.
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:param member_name: The member of the module to return. If empty or
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None, get() will return the module itself.
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:param help: Help text for this entry. This may be a string or
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:param info: More information for this entry. Registry.get_info()
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can be used to get this information. Registry treats this as an
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opaque storage location (it is defined by the caller).
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:param info: More information for this entry. Registry
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:param override_existing: If True, replace the existing object
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with the new one. If False, if there is already something
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registered with the same key, raise a KeyError
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self._dict[key] = _LazyObjectGetter(module_name, member_name)
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self._add_help_and_info(key, help=help, info=info)
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def register_alias(self, key, target, info=None):
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"""Register an alias.
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:param key: Alias name
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:param target: Target key name
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if key in self._dict and key not in self._aliases:
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raise KeyError('Key %r already registered and not an alias' % key)
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self._dict[key] = self._dict[target]
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self._aliases[key] = target
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info = self._info_dict[target]
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self._add_help_and_info(key, help=self._help_dict[target], info=info)
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def _add_help_and_info(self, key, help=None, info=None):
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"""Add the help and information about this key"""
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self._help_dict[key] = help
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return self._dict[self._get_key_or_default(key)].get_obj()
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def _get_module(self, key):
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"""Return the module the object will be or was loaded from.
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:param key: The key to obtain the module for.
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:return: The name of the module
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return self._dict[key].get_module()
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def get_prefix(self, fullname):
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"""Return an object whose key is a prefix of the supplied value.
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"""Get a list of registered entries"""
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return sorted(self._dict)
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return sorted(self._dict.keys())
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def iteritems(self):
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for key in self._dict:
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yield key, self._dict[key].get_obj()
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for key, getter in self._dict.iteritems():
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yield key, getter.get_obj()
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# We should not use the iteritems() implementation below (see bug
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return [(key, self._dict[key].get_obj()) for key in self.keys()]
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return sorted(self.iteritems())
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def _set_default_key(self, key):
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if key not in self._dict:
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if not self._dict.has_key(key):
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raise KeyError('No object registered under key %s.' % key)
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self._default_key = key
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return self._default_key
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default_key = property(_get_default_key, _set_default_key,
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doc="Current value of the default key."
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" Can be set to any existing key.")
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doc="Current value of the default key."
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" Can be set to any existing key.")
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class FormatRegistry(Registry):
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Registry.__init__(self)
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self._other_registry = other_registry
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def register(self, key, obj, help=None, info=None,
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override_existing=False):
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Registry.register(self, key, obj, help=help, info=info,
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override_existing=override_existing)
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if self._other_registry is not None:
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self._other_registry.register(key, obj, help=help,
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info=info, override_existing=override_existing)
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def register_lazy(self, key, module_name, member_name,
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help=None, info=None,
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override_existing=False):
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# Overridden to allow capturing registrations to two seperate
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# registries in a single call.
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Registry.register_lazy(self, key, module_name, member_name,
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help=help, info=info, override_existing=override_existing)
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help=help, info=info, override_existing=override_existing)
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if self._other_registry is not None:
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self._other_registry.register_lazy(key, module_name, member_name,
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help=help, info=info, override_existing=override_existing)
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def remove(self, key):
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Registry.remove(self, key)
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if self._other_registry is not None:
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self._other_registry.remove(key)
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help=help, info=info, override_existing=override_existing)
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def get(self, format_string):
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r = Registry.get(self, format_string)