Python - Context Managers : Efficiently Managing Resources

** Context Managers - Efficiently Managing Resources


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class Open_File():

def __init__(self, filename, mode):
self.filename = filename
self.mode = mode

def __enter__(self):
self.file = open(self.filename, self.mode)
return self.file

def __exit__(self, exc_type, exc_val, traceback):
self.file.close()


with Open_File('sample.txt', 'w') as f:
f.write('Testing')


print(f.closed)

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True

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Testing  <~~ sample.txt

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from contextlib import contextmanager


@contextmanager
def open_file(file, mode):
    f = open(file, mode)
    yield f
    f.close()


with open_file('sample.txt', 'w') as f:
    f.write('Hi, LinuxerHAN !!')

print(f.closed)

---------------------------------

True

---------------------------------

Hi, LinuxerHAN !!  <~~ sample.txt

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import os
from contextlib import contextmanager


cwd = os.getcwd()
os.chdir('Sample-Dir-One')
print(os.listdir())
os.chdir(cwd)

cwd = os.getcwd()
os.chdir('Sample-Dir-Two')
print(os.listdir())
os.chdir(cwd)

---------------------------------

['1-1.txt', '1-2.txt', '1-3.txt']
['2-1.txt', '2-2.txt', '2-3.txt']

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==========================================

import os
from contextlib import contextmanager


@contextmanager
def change_dir(destination):
try:
cwd = os.getcwd()
os.chdir(destination)
yield

finally:
os.chdir(cwd)

with change_dir('Sample-Dir-One'):
print(os.listdir())

with change_dir('Sample-Dir-Two'):
print(os.listdir())

---------------------------------

['1-1.txt', '1-2.txt', '1-3.txt']
['2-1.txt', '2-2.txt', '2-3.txt']

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