from mirror import LookingGlass manager = LookingGlass() manager monster = manager.__enter__() monster == 'JABBERWOCKY' monster manager manager.__exit__(None, None, None) monster
with open('mirror.py') as fp:
src = fp.read(60)
len(src) # 60
fp # <_io.TextIOWrapper name='mirror.py' mode='r' encoding='cp949'>
fp.closed, fp.encoding # (True, 'cp949')
fp.read(60) # 더이상 파일 입출력은 할 수 없다
from mirror import LookingGlass
with LookingGlass() as what:
print('ABCDEFG') # GFEDCBA; 역순
print(1 / 0)
print(what) # YKCOWREBBAJ; 역순
print(what) # JABBERWOCKY; 정상
# with 문 없이도 컨텍스트 매니저를 사용할 수 있다
from mirror import LookingGlass
manager = LookingGlass() # <1>
manager
monster = manager.__enter__() # <2>
monster == 'JABBERWOCKY' # <3> eurT ; 여기서 출력함수가 멍키패칭됨
monster #'YKCOWREBBAJ
manager.__exit__(None, None, None) # <4>
monster # 'JABBERWOCKY'; 출력함수 정상
@author: jiyun
"""
# 원서 기준 449~453p
with open('mirror.py') as fp:
src = fp.read(60)
print(len(src)) #60
print(fp) # 변수로 살아있음
print(fp.closed, fp.encoding) # 속성 읽기 가능
#print(fp.read(60)) # 파일 닫아서 입출력은 불가능
from mirror import LookingGlass
with LookingGlass() as what:
print('ABCDEFGHIGKLMNOPQRSTUVWXYZ') # ZYXWVUTSRQPONMLKGIHGFEDCBA
print(what) # YKCOWREBBAJ
print(what) # enter가 반환한 JABBERWOCKY
print('ABCDEFGHIGKLMNOPQRSTUVWXYZ') # ABCDEFGHIGKLMNOPQRSTUVWXYZ
"""
class LookingGlass:
def __enter__(self):
import sys
self.original_write = sys.stdout.write
sys.stdout.write = self.reverse_write
return 'JABBERWOCKY'
def reverse_write(self, text):
def reverse_write(self, text):
self.original_write(text[::-1])
def __exit__(self, exc_type, exc_value, traceback):
import sys
sys.stdout.write = self.original_write
if exc_type is ZeroDivisionError:
print('Please DO NOT divide by zero!')
return True
#Example 15-4: Exercising LookingGlass class w/o a with block
from mirror import LookingGlass
manager = LookingGlass()
manager
#<__main__.LookingGlass object at 0x0000021BF1B83588>
monster = manager.__enter__()
monster == 'JABBERWOCKY'
#eurT
monster
#'YKCOWREBBAJ'
manager
#>88538B1FB1200000x0 ta tcejbo ssalGgnikooL.__niam__<
manager.__exit__(None, None, None)
monster
#'JABBERWOCKY
#Example 15-5:
def __enter__(self): ➊#调用 __enter__ 方法时不传入其他参数
import sys
self.original_write = sys.stdout.write ➋
sys.stdout.write = self.reverse_write ➌#替换标准输出为reverse
return 'JABBERWOCKY' ➍#print(what)回调用标准输出
def reverse_write(self, text): ➎
self.original_write(text[::-1])
def __exit__(self, exc_type, exc_value, traceback): ➏
import sys ➐
sys.stdout.write = self.original_write ➑#把标准输出改回原来的
if exc_type is ZeroDivisionError: ➒
print('Please DO NOT divide by zero!')
return True ➓
>> from mirror import LookingGlass
>>> with LookingGlass() as what: ➊
... print('Alice, Kitty and Snowdrop') ➋
... print(what)
...
pordwonS dna yttiK ,ecilA ➌
YKCOWREBBAJ
>>> what ➍
'JABBERWOCKY'
>>> from mirror import LookingGlass
>>> manager = LookingGlass() ➊
>>> manager
<mirror.LookingGlass object at 0x2a578ac>
>>> monster = manager.__enter__() ➋
>>> monster == 'JABBERWOCKY' ➌
eurT
from mirror import LookingGlass
import sys
with LookingGlass() as enterResult:
sys.stdout.write(enterResult)
sys.stdout.write("\n")
sys.stdout.write("It is reversed")
sys.stdout.write("\n")
#a = 5 / 0
sys.stdout.write("It is normal\n")
## Test driving the LookingGLass context managers class
from mirror import LookingGlass
with LookingGlass() as what:
print('AKshat', 'ROnaldo', 'Batman')
print(what)
## Exercising LookingGlass without a with block
from mirror import LookingGlass
manager = LookingGlass()
manager
monster = manager.__enter__()
monster == 'JABBEREOCKY'