80 lines
1.7 KiB
Python
80 lines
1.7 KiB
Python
"""
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A "mirroring" ``stdout`` context manager.
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While active, the context manager reverses text output to
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``stdout``::
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# tag::MIRROR_GEN_DEMO_1[]
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>>> from mirror_gen import looking_glass
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>>> with looking_glass() as what: # <1>
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... print('Alice, Kitty and Snowdrop')
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... print(what)
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...
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pordwonS dna yttiK ,ecilA
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YKCOWREBBAJ
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>>> what
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'JABBERWOCKY'
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>>> print('back to normal')
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back to normal
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# end::MIRROR_GEN_DEMO_1[]
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This exposes the context manager operation::
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# tag::MIRROR_GEN_DEMO_2[]
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>>> from mirror_gen import looking_glass
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>>> manager = looking_glass() # <1>
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>>> manager # doctest: +ELLIPSIS
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<contextlib._GeneratorContextManager object at 0x...>
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>>> monster = manager.__enter__() # <2>
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>>> monster == 'JABBERWOCKY' # <3>
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eurT
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>>> monster
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'YKCOWREBBAJ'
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>>> manager # doctest: +ELLIPSIS
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>...x0 ta tcejbo reganaMtxetnoCrotareneG_.biltxetnoc<
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>>> manager.__exit__(None, None, None) # <4>
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False
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>>> monster
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'JABBERWOCKY'
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# end::MIRROR_GEN_DEMO_2[]
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The decorated generator also works as a decorator:
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# tag::MIRROR_GEN_DECO[]
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>>> @looking_glass()
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... def verse():
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... print('The time has come')
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...
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>>> verse() # <1>
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emoc sah emit ehT
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>>> print('back to normal') # <2>
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back to normal
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# end::MIRROR_GEN_DECO[]
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"""
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# tag::MIRROR_GEN_EX[]
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import contextlib
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import sys
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@contextlib.contextmanager # <1>
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def looking_glass():
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original_write = sys.stdout.write # <2>
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def reverse_write(text): # <3>
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original_write(text[::-1])
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sys.stdout.write = reverse_write # <4>
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yield 'JABBERWOCKY' # <5>
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sys.stdout.write = original_write # <6>
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# end::MIRROR_GEN_EX[]
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