1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
|
# Copyright (C) 2006 by Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""Functionality to create lazy evaluation objects.
This includes waiting to import a module until it is actually used.
"""
import sys
class ScopeReplacer(object):
"""A lazy object that will replace itself in the appropriate scope.
This object sits, ready to create the real object the first time it is
needed.
"""
__slots__ = ('_scope', '_factory', '_name')
def __init__(self, scope, factory, name):
"""Create a temporary object in the specified scope.
Once used, a real object will be placed in the scope.
:param scope: The scope the object should appear in
:param factory: A callable that will create the real object.
It will be passed (self, scope, name)
:param name: The variable name in the given scope.
"""
self._scope = scope
self._factory = factory
self._name = name
scope[name] = self
def _replace(self):
"""Actually replace self with other in the given scope"""
factory = object.__getattribute__(self, '_factory')
scope = object.__getattribute__(self, '_scope')
name = object.__getattribute__(self, '_name')
obj = factory(self, scope, name)
scope[name] = obj
return obj
def _cleanup(self):
"""Stop holding on to all the extra stuff"""
del self._factory
del self._scope
del self._name
def __getattribute__(self, attr):
obj = object.__getattribute__(self, '_replace')()
object.__getattribute__(self, '_cleanup')()
return getattr(obj, attr)
def __call__(self, *args, **kwargs):
obj = object.__getattribute__(self, '_replace')()
object.__getattribute__(self, '_cleanup')()
return obj(*args, **kwargs)
class ImportReplacer(ScopeReplacer):
"""This is designed to replace only a portion of an import list.
It will replace itself with a module, and then make children
entries also ImportReplacer objects.
At present, this only supports 'import foo.bar.baz' syntax.
"""
# Intentially a long semi-unique name that won't likely exist
# elsewhere. (We can't use isinstance because that accesses __class__
# which causes the __getattribute__ to trigger)
__slots__ = ('_import_replacer_children', '_member', '_module_path')
def __init__(self, scope, name, module_path, member=None, children=[]):
"""Upon request import 'module_path' as the name 'module_name'.
When imported, prepare children to also be imported.
:param scope: The scope that objects should be imported into.
Typically this is globals()
:param name: The variable name. Often this is the same as the
module_path. 'bzrlib'
:param module_path: A list for the fully specified module path
['bzrlib', 'foo', 'bar']
:param member: The member inside the module to import, often this is
None, indicating the module is being imported.
:param children: Children entries to be imported later.
This should be a list of children specifications.
[('foo', 'bzrlib.foo', [('bar', 'bzrlib.foo.bar'),])]
Examples:
import foo => name='foo' module_path='foo',
member=None, children=[]
import foo.bar => name='foo' module_path='foo', member=None,
children=[('bar', 'foo.bar', [])]
from foo import bar => name='bar' module_path='foo', member='bar'
children=[]
from foo import bar, baz would get translated into 2 import
requests. On for 'name=bar' and one for 'name=baz'
"""
if member is not None:
assert not children, \
'Cannot supply both a member and children'
self._import_replacer_children = children
self._member = member
self._module_path = module_path
# Indirecting through __class__ so that children can
# override _import (especially our instrumented version)
cls = object.__getattribute__(self, '__class__')
ScopeReplacer.__init__(self, scope=scope, name=name,
factory=cls._import)
def _import(self, scope, name):
children = object.__getattribute__(self, '_import_replacer_children')
member = object.__getattribute__(self, '_member')
module_path = object.__getattribute__(self, '_module_path')
module_python_path = '.'.join(module_path)
if member is not None:
module = __import__(module_python_path, scope, scope, [member])
return getattr(module, member)
else:
module = __import__(module_python_path, scope, scope, [])
for path in module_path[1:]:
module = getattr(module, path)
# Prepare the children to be imported
for child_name, child_path, grandchildren in children:
ImportReplacer(module.__dict__, name=child_name,
module_path=child_path, member=None,
children=grandchildren)
return module
|