Creating Custom Context Managers 관련

Context Managers and Python's with Statement

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In this step-by-step tutorial, you'll learn what the Python with statement is and how to use it with existing context managers. You'll also learn how to create your own context managers.

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Context Managers and Python's with Statement

In this step-by-step tutorial, you'll learn what the Python with statement is and how to use it with existing context managers. You'll also learn how to create your own context managers.

You’ve already worked with context managers from the standard library and third-party libraries. There’s nothing special or magical about open(), threading.Lock, decimal.localcontext(), or the others. They just return objects that implement the context management protocol.

You can provide the same functionality by implementing both the .__enter__() and the .__exit__() special methods in your class-based context managers. You can also create custom function-based context managers using the contextlib.contextmanager decorator from the standard library and an appropriately coded generator function.

In general, context managers and the with statement aren’t limited to resource management. They allow you to provide and reuse common setup and teardown code. In other words, with context managers, you can perform any pair of operations that needs to be done before and after another operation or procedure, such as:

• Open and close
• Lock and release
• Change and reset
• Create and delete
• Enter and exit
• Start and stop
• Setup and teardown

You can provide code to safely manage any of these pairs of operations in a context manager. Then you can reuse that context manager in with statements throughout your code. This prevents errors and reduces repetitive boilerplate code. It also makes your APIs safer, cleaner, and more user-friendly.

In the next two sections, you’ll learn the basics of creating class-based and function-based context managers.