Python context manager examples

context_manager.py

import json
from contextlib import contextmanager

data = {'key': 1234}

with open('the_json_file.json', 'wt') as json_file:
	json.dump(data, json_file)	

with OpenFile('the_json_file.json', 'wt') as json_file:
	json.dump(data, json_file)	
	
with open_file('the_json_file.json', 'wt') as json_file:
	json.dump(data, json_file)	
	
	
# Version 1
class OpenFile:
    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):
        self.file.close()

# Version 2
@contextmanager
def open_file(filename, mode):
    file = open(filename, mode)
    yield file
    file.close()