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