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ch11-24: clean up by @eumiro & sync with Atlas

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Luciano Ramalho
2021-02-14 20:58:46 -03:00
parent 03ace4f4ae
commit 47cafc801a
143 changed files with 21692 additions and 63 deletions
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4
18-context-mngr/README.rst Normal file
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Sample code for Chapter 15 - "Context managers and something else"
From the book "Fluent Python" by Luciano Ramalho (O'Reilly, 2015)
http://shop.oreilly.com/product/0636920032519.do

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18-context-mngr/mirror.py Normal file
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"""
A "mirroring" ``stdout`` context.
While active, the context manager reverses text output to
``stdout``::
# tag::MIRROR_DEMO_1[]
>>> from mirror import LookingGlass
>>> with LookingGlass() as what: # <1>
... print('Alice, Kitty and Snowdrop') # <2>
... print(what)
...
pordwonS dna yttiK ,ecilA # <3>
YKCOWREBBAJ
>>> what # <4>
'JABBERWOCKY'
>>> print('Back to normal.') # <5>
Back to normal.
# end::MIRROR_DEMO_1[]
This exposes the context manager operation::
# tag::MIRROR_DEMO_2[]
>>> from mirror import LookingGlass
>>> manager = LookingGlass() # <1>
>>> manager
<mirror.LookingGlass object at 0x2a578ac>
>>> monster = manager.__enter__() # <2>
>>> monster == 'JABBERWOCKY' # <3>
eurT
>>> monster
'YKCOWREBBAJ'
>>> manager
>ca875a2x0 ta tcejbo ssalGgnikooL.rorrim<
>>> manager.__exit__(None, None, None) # <4>
>>> monster
'JABBERWOCKY'
# end::MIRROR_DEMO_2[]
The context manager can handle and "swallow" exceptions.
# tag::MIRROR_DEMO_3[]
>>> from mirror import LookingGlass
>>> with LookingGlass():
... print('Humpty Dumpty')
... x = 1/0 # <1>
... print('END') # <2>
...
ytpmuD ytpmuH
Please DO NOT divide by zero!
>>> with LookingGlass():
... print('Humpty Dumpty')
... x = no_such_name # <1>
... print('END') # <2>
...
Traceback (most recent call last):
...
NameError: name 'no_such_name' is not defined
# end::MIRROR_DEMO_3[]
"""
# tag::MIRROR_EX[]
class LookingGlass:
def __enter__(self): # <1>
import sys
self.original_write = sys.stdout.write # <2>
sys.stdout.write = self.reverse_write # <3>
return 'JABBERWOCKY' # <4>
def reverse_write(self, text): # <5>
self.original_write(text[::-1])
def __exit__(self, exc_type, exc_value, traceback): # <6>
import sys # <7>
sys.stdout.write = self.original_write # <8>
if exc_type is ZeroDivisionError: # <9>
print('Please DO NOT divide by zero!')
return True # <10>
# <11>
# end::MIRROR_EX[]

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18-context-mngr/mirror_gen.py Normal file
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"""
A "mirroring" ``stdout`` context manager.
While active, the context manager reverses text output to
``stdout``::
# tag::MIRROR_GEN_DEMO_1[]
>>> from mirror_gen import looking_glass
>>> with looking_glass() as what: # <1>
... print('Alice, Kitty and Snowdrop')
... print(what)
...
pordwonS dna yttiK ,ecilA
YKCOWREBBAJ
>>> what
'JABBERWOCKY'
# end::MIRROR_GEN_DEMO_1[]
This exposes the context manager operation::
# tag::MIRROR_GEN_DEMO_2[]
>>> from mirror_gen import looking_glass
>>> manager = looking_glass() # <1>
>>> manager # doctest: +ELLIPSIS
<contextlib._GeneratorContextManager object at 0x...>
>>> monster = manager.__enter__() # <2>
>>> monster == 'JABBERWOCKY' # <3>
eurT
>>> monster
'YKCOWREBBAJ'
>>> manager # doctest: +ELLIPSIS
>...x0 ta tcejbo reganaMtxetnoCrotareneG_.biltxetnoc<
>>> manager.__exit__(None, None, None) # <4>
>>> monster
'JABBERWOCKY'
# end::MIRROR_GEN_DEMO_2[]
"""
# tag::MIRROR_GEN_EX[]
import contextlib
@contextlib.contextmanager # <1>
def looking_glass():
import sys
original_write = sys.stdout.write # <2>
def reverse_write(text): # <3>
original_write(text[::-1])
sys.stdout.write = reverse_write # <4>
yield 'JABBERWOCKY' # <5>
sys.stdout.write = original_write # <6>
# end::MIRROR_GEN_EX[]

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18-context-mngr/mirror_gen_exc.py Normal file
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"""
A "mirroring" ``stdout`` context manager.
While active, the context manager reverses text output to
``stdout``::
# tag::MIRROR_GEN_DEMO_1[]
>>> from mirror_gen import looking_glass
>>> with looking_glass() as what: # <1>
... print('Alice, Kitty and Snowdrop')
... print(what)
...
pordwonS dna yttiK ,ecilA
YKCOWREBBAJ
>>> what
'JABBERWOCKY'
# end::MIRROR_GEN_DEMO_1[]
This exposes the context manager operation::
# tag::MIRROR_GEN_DEMO_2[]
>>> from mirror_gen import looking_glass
>>> manager = looking_glass() # <1>
>>> manager # doctest: +ELLIPSIS
<contextlib._GeneratorContextManager object at 0x...>
>>> monster = manager.__enter__() # <2>
>>> monster == 'JABBERWOCKY' # <3>
eurT
>>> monster
'YKCOWREBBAJ'
>>> manager # doctest: +ELLIPSIS
>...x0 ta tcejbo reganaMtxetnoCrotareneG_.biltxetnoc<
>>> manager.__exit__(None, None, None) # <4>
>>> monster
'JABBERWOCKY'
# end::MIRROR_GEN_DEMO_2[]
The context manager can handle and "swallow" exceptions.
The following test does not pass under doctest (a
ZeroDivisionError is reported by doctest) but passes
if executed by hand in the Python 3 console (the exception
is handled by the context manager):
# tag::MIRROR_GEN_DEMO_3[]
>>> from mirror_gen import looking_glass
>>> with looking_glass():
... print('Humpty Dumpty')
... x = 1/0 # <1>
... print('END') # <2>
...
ytpmuD ytpmuH
Please DO NOT divide by zero!
# end::MIRROR_GEN_DEMO_3[]
>>> with looking_glass():
... print('Humpty Dumpty')
... x = no_such_name # <1>
... print('END') # <2>
...
Traceback (most recent call last):
...
NameError: name 'no_such_name' is not defined
"""
# tag::MIRROR_GEN_EXC[]
import contextlib
@contextlib.contextmanager
def looking_glass():
import sys
original_write = sys.stdout.write
def reverse_write(text):
original_write(text[::-1])
sys.stdout.write = reverse_write
msg = '' # <1>
try:
yield 'JABBERWOCKY'
except ZeroDivisionError: # <2>
msg = 'Please DO NOT divide by zero!'
finally:
sys.stdout.write = original_write # <3>
if msg:
print(msg) # <4>
# end::MIRROR_GEN_EXC[]