What is the protocol implemented by the context manager in Python?

In Python, a protocol implemented by a context manager is a set of methods that allow an object to be used in a with statement. Such an object must implement the __enter__() and __exit__() methods.

• __enter__() is called when entering the with block. It typically prepares the resource and can return an object that will be accessible inside the block.
• __exit__(exc_type, exc_val, exc_tb) is called when exiting the with block, even if an exception occurs inside the block. It is responsible for releasing resources and handling exceptions.

Example:

class FileManager:
    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, exc_tb):
        self.file.close()
        # Return False to not suppress exceptions
        return False

with FileManager('test.txt', 'w') as f:
    f.write('Example of using a context manager')

Thus, the context manager protocol provides convenient and safe resource management.