10.3 Context Managers

Learning context managers and the "with" statement for safe management of resources like files and network connections.

Context managers are a powerful Python feature used for efficient resource management. They ensure that resources (like files, database connections, or locks in multi-threaded applications) are properly initialized and, most importantly, automatically released (cleaned up), even if an error occurs during their use. This is achieved through the `with` statement and objects that implement the "context manager protocol," namely the special methods `__enter__()` and `__exit__()`.

class MyContextManager:
    def __enter__(self):
        print("Entering the context (e.g., opening a resource).")
        # The resource could be returned here
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        # exc_type, exc_val, exc_tb will have values if an error occurred
        print("Exiting the context (e.g., closing the resource).")
        if exc_type:
            print(f"An exception occurred: {exc_type.__name__}")
        # If we return True from here, the exception is "suppressed"
        return False

with MyContextManager() as manager:
    print("Inside the 'with' block. The resource is now available.")
    # uncomment to see exception handling:
    # raise ValueError("Simulating an error")

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