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