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79 lines
2.7 KiB
79 lines
2.7 KiB
5 years ago
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"""Faux ``threading`` version using ``dummy_thread`` instead of ``thread``.
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The module ``_dummy_threading`` is added to ``sys.modules`` in order
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to not have ``threading`` considered imported. Had ``threading`` been
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directly imported it would have made all subsequent imports succeed
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regardless of whether ``thread`` was available which is not desired.
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"""
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from sys import modules as sys_modules
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import dummy_thread
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# Declaring now so as to not have to nest ``try``s to get proper clean-up.
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holding_thread = False
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holding_threading = False
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holding__threading_local = False
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try:
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# Could have checked if ``thread`` was not in sys.modules and gone
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# a different route, but decided to mirror technique used with
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# ``threading`` below.
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if 'thread' in sys_modules:
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held_thread = sys_modules['thread']
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holding_thread = True
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# Must have some module named ``thread`` that implements its API
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# in order to initially import ``threading``.
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sys_modules['thread'] = sys_modules['dummy_thread']
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if 'threading' in sys_modules:
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# If ``threading`` is already imported, might as well prevent
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# trying to import it more than needed by saving it if it is
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# already imported before deleting it.
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held_threading = sys_modules['threading']
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holding_threading = True
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del sys_modules['threading']
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if '_threading_local' in sys_modules:
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# If ``_threading_local`` is already imported, might as well prevent
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# trying to import it more than needed by saving it if it is
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# already imported before deleting it.
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held__threading_local = sys_modules['_threading_local']
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holding__threading_local = True
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del sys_modules['_threading_local']
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import threading
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# Need a copy of the code kept somewhere...
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sys_modules['_dummy_threading'] = sys_modules['threading']
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del sys_modules['threading']
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sys_modules['_dummy__threading_local'] = sys_modules['_threading_local']
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del sys_modules['_threading_local']
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from _dummy_threading import *
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from _dummy_threading import __all__
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finally:
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# Put back ``threading`` if we overwrote earlier
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if holding_threading:
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sys_modules['threading'] = held_threading
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del held_threading
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del holding_threading
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# Put back ``_threading_local`` if we overwrote earlier
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if holding__threading_local:
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sys_modules['_threading_local'] = held__threading_local
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del held__threading_local
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del holding__threading_local
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# Put back ``thread`` if we overwrote, else del the entry we made
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if holding_thread:
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sys_modules['thread'] = held_thread
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del held_thread
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else:
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del sys_modules['thread']
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del holding_thread
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del dummy_thread
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del sys_modules
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