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