# File management using context manager
class FileManager():
    def __init__(self, filename, mode):
        self.filename = filename
        self.mode = mode
        self.file = None
  
    # The __enter__ method opens the file and returns a file object
    def __enter__(self):
        print('Open file: {}'.format(self.filename))
        self.file = open(self.filename, self.mode)
        return self.file

    # The __exit__ method takes care of closing the file on exiting the with block 
    def __exit__(self, etype, value, traceback):
        print('Close file: {}'.format(self.filename))
        self.file.close()

# A FileManager object is created with test.txt as the filename and "write" mode
# when __init__ method is executed
with FileManager('test.txt', 'w') as f:
    f.write('First line\n')
    f.write('Second line\n')

# The file is already closed thanks to the automatic call to the __exit__ method
print('File closed: {}\n'.format(f.closed))

with FileManager('test.txt', 'r') as f:
    for line in f:
        print(line.rstrip())

# Output
#Open file: test.txt
#Close file: test.txt
#File closed: True
#
#Open file: test.txt
#First line
#Second line
#Close file: test.txt