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# Copyright 2009 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Id$
__all__ = ['lazyimport']
import sys
import types
from portage.proxy.objectproxy import ObjectProxy
_module_proxies = {}
def _register_module_proxy(name, proxy):
proxy_list = _module_proxies.get(name)
if proxy_list is None:
proxy_list = []
_module_proxies[name] = proxy_list
proxy_list.append(proxy)
def _unregister_module_proxy(name):
"""
Destroy all proxies that reference the give module name. Also, check
for other proxies referenced by modules that have been imported and
destroy those proxies too. This way, destruction of a single proxy
can trigger destruction of all the rest.
"""
proxy_list = _module_proxies.get(name)
if proxy_list is not None:
del _module_proxies[name]
for proxy in proxy_list:
object.__getattribute__(proxy, '_get_target')()
modules = sys.modules
for name, proxy_list in list(_module_proxies.iteritems()):
if name not in modules:
continue
del _module_proxies[name]
for proxy in proxy_list:
object.__getattribute__(proxy, '_get_target')()
class _LazyImport(ObjectProxy):
__slots__ = ('_scope', '_alias', '_name', '_target')
def __init__(self, scope, alias, name):
ObjectProxy.__init__(self)
object.__setattr__(self, '_scope', scope)
object.__setattr__(self, '_alias', alias)
object.__setattr__(self, '_name', name)
_register_module_proxy(name, self)
def _get_target(self):
try:
return object.__getattribute__(self, '_target')
except AttributeError:
pass
name = object.__getattribute__(self, '_name')
__import__(name)
target = sys.modules[name]
object.__setattr__(self, '_target', target)
object.__getattribute__(self, '_scope')[
object.__getattribute__(self, '_alias')] = target
_unregister_module_proxy(name)
return target
class _LazyImportFrom(_LazyImport):
__slots__ = ('_attr_name',)
def __init__(self, scope, name, attr_name, alias):
object.__setattr__(self, '_attr_name', attr_name)
_LazyImport.__init__(self, scope, alias, name)
def _get_target(self):
try:
return object.__getattribute__(self, '_target')
except AttributeError:
pass
name = object.__getattribute__(self, '_name')
attr_name = object.__getattribute__(self, '_attr_name')
__import__(name)
target = getattr(sys.modules[name], attr_name)
object.__setattr__(self, '_target', target)
object.__getattribute__(self, '_scope')[
object.__getattribute__(self, '_alias')] = target
_unregister_module_proxy(name)
return target
def lazyimport(scope, *args):
"""
Create a proxy in the given scope in order to performa a lazy import.
Syntax Result
foo import foo
foo:bar,baz from foo import bar, baz
foo:bar@baz from foo import bar as baz
@param scope: the scope in which to place the import, typically globals()
@type myfilename: dict
@param args: module names to import
@type args: strings
"""
modules = sys.modules
for s in args:
parts = s.split(':', 1)
if len(parts) == 1:
name = s
if not name or not isinstance(name, basestring):
raise ValueError(name)
components = name.split('.')
parent_scope = scope
for i in xrange(len(components)):
alias = components[i]
if i < len(components) - 1:
parent_name = ".".join(components[:i+1])
__import__(parent_name)
mod = modules.get(parent_name)
if not isinstance(mod, types.ModuleType):
# raise an exception
__import__(name)
parent_scope[alias] = mod
parent_scope = mod.__dict__
continue
already_imported = modules.get(name)
if already_imported is not None:
parent_scope[alias] = already_imported
else:
parent_scope[alias] = \
_LazyImport(parent_scope, alias, name)
else:
name, fromlist = parts
already_imported = modules.get(name)
fromlist = fromlist.split(',')
for s in fromlist:
alias = s.split('@', 1)
if len(alias) == 1:
alias = alias[0]
attr_name = alias
else:
attr_name, alias = alias
if already_imported is not None:
try:
scope[alias] = getattr(already_imported, attr_name)
except AttributeError:
raise ImportError('cannot import name %s' % attr_name)
else:
scope[alias] = \
_LazyImportFrom(scope, name, attr_name, alias)
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