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920dae64 AT |
1 | """Faux ``threading`` version using ``dummy_thread`` instead of ``thread``. |
2 | ||
3 | The module ``_dummy_threading`` is added to ``sys.modules`` in order | |
4 | to not have ``threading`` considered imported. Had ``threading`` been | |
5 | directly imported it would have made all subsequent imports succeed | |
6 | regardless of whether ``thread`` was available which is not desired. | |
7 | ||
8 | :Author: Brett Cannon | |
9 | :Contact: brett@python.org | |
10 | ||
11 | XXX: Try to get rid of ``_dummy_threading``. | |
12 | ||
13 | """ | |
14 | from sys import modules as sys_modules | |
15 | ||
16 | import dummy_thread | |
17 | ||
18 | # Declaring now so as to not have to nest ``try``s to get proper clean-up. | |
19 | holding_thread = False | |
20 | holding_threading = False | |
21 | holding__threading_local = False | |
22 | ||
23 | try: | |
24 | # Could have checked if ``thread`` was not in sys.modules and gone | |
25 | # a different route, but decided to mirror technique used with | |
26 | # ``threading`` below. | |
27 | if 'thread' in sys_modules: | |
28 | held_thread = sys_modules['thread'] | |
29 | holding_thread = True | |
30 | # Must have some module named ``thread`` that implements its API | |
31 | # in order to initially import ``threading``. | |
32 | sys_modules['thread'] = sys_modules['dummy_thread'] | |
33 | ||
34 | if 'threading' in sys_modules: | |
35 | # If ``threading`` is already imported, might as well prevent | |
36 | # trying to import it more than needed by saving it if it is | |
37 | # already imported before deleting it. | |
38 | held_threading = sys_modules['threading'] | |
39 | holding_threading = True | |
40 | del sys_modules['threading'] | |
41 | ||
42 | if '_threading_local' in sys_modules: | |
43 | # If ``_threading_local`` is already imported, might as well prevent | |
44 | # trying to import it more than needed by saving it if it is | |
45 | # already imported before deleting it. | |
46 | held__threading_local = sys_modules['_threading_local'] | |
47 | holding__threading_local = True | |
48 | del sys_modules['_threading_local'] | |
49 | ||
50 | import threading | |
51 | # Need a copy of the code kept somewhere... | |
52 | sys_modules['_dummy_threading'] = sys_modules['threading'] | |
53 | del sys_modules['threading'] | |
54 | sys_modules['_dummy__threading_local'] = sys_modules['_threading_local'] | |
55 | del sys_modules['_threading_local'] | |
56 | from _dummy_threading import * | |
57 | from _dummy_threading import __all__ | |
58 | ||
59 | finally: | |
60 | # Put back ``threading`` if we overwrote earlier | |
61 | ||
62 | if holding_threading: | |
63 | sys_modules['threading'] = held_threading | |
64 | del held_threading | |
65 | del holding_threading | |
66 | ||
67 | # Put back ``_threading_local`` if we overwrote earlier | |
68 | ||
69 | if holding__threading_local: | |
70 | sys_modules['_threading_local'] = held__threading_local | |
71 | del held__threading_local | |
72 | del holding__threading_local | |
73 | ||
74 | # Put back ``thread`` if we overwrote, else del the entry we made | |
75 | if holding_thread: | |
76 | sys_modules['thread'] = held_thread | |
77 | del held_thread | |
78 | else: | |
79 | del sys_modules['thread'] | |
80 | del holding_thread | |
81 | ||
82 | del dummy_thread | |
83 | del sys_modules |