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 """ 9 from sys import modules as sys_modules 10 11 import dummy_thread 12 13 # Declaring now so as to not have to nest ``try``s to get proper clean-up. 14 holding_thread = False 15 holding_threading = False 16 holding__threading_local = False 17 18 try: 19 # Could have checked if ``thread`` was not in sys.modules and gone 20 # a different route, but decided to mirror technique used with 21 # ``threading`` below. 22 if 'thread' in sys_modules: 23 held_thread = sys_modules['thread'] 24 holding_thread = True 25 # Must have some module named ``thread`` that implements its API 26 # in order to initially import ``threading``. 27 sys_modules['thread'] = sys_modules['dummy_thread'] 28 29 if 'threading' in sys_modules: 30 # If ``threading`` is already imported, might as well prevent 31 # trying to import it more than needed by saving it if it is 32 # already imported before deleting it. 33 held_threading = sys_modules['threading'] 34 holding_threading = True 35 del sys_modules['threading'] 36 37 if '_threading_local' in sys_modules: 38 # If ``_threading_local`` is already imported, might as well prevent 39 # trying to import it more than needed by saving it if it is 40 # already imported before deleting it. 41 held__threading_local = sys_modules['_threading_local'] 42 holding__threading_local = True 43 del sys_modules['_threading_local'] 44 45 import threading 46 # Need a copy of the code kept somewhere... 47 sys_modules['_dummy_threading'] = sys_modules['threading'] 48 del sys_modules['threading'] 49 sys_modules['_dummy__threading_local'] = sys_modules['_threading_local'] 50 del sys_modules['_threading_local'] 51 from _dummy_threading import * 52 from _dummy_threading import __all__ 53 54 finally: 55 # Put back ``threading`` if we overwrote earlier 56 57 if holding_threading: 58 sys_modules['threading'] = held_threading 59 del held_threading 60 del holding_threading 61 62 # Put back ``_threading_local`` if we overwrote earlier 63 64 if holding__threading_local: 65 sys_modules['_threading_local'] = held__threading_local 66 del held__threading_local 67 del holding__threading_local 68 69 # Put back ``thread`` if we overwrote, else del the entry we made 70 if holding_thread: 71 sys_modules['thread'] = held_thread 72 del held_thread 73 else: 74 del sys_modules['thread'] 75 del holding_thread 76 77 del dummy_thread 78 del sys_modules 79
