Fluent Python: Clear, Concise, and Effective Programming

by Luciano Ramalho

Using @contextmanager The @contextmanager decorator is an elegant and practical tool that brings together three distinctive Python features: a function decorator, a generator, and the with statement. Using @contextmanager reduces the boilerplate of creating a context manager: instead of writing a whole class with __enter__/__exit__ methods, you just implement a generator with a single yield that should produce whatever you want the __enter__ method to return. In a generator decorated with @contextmanager, yield splits the body of the function in two parts: everything before the yield will be executed at the beginning of the with block when the interpreter calls __enter__; the code after yield will run when __exit__ is called at the end of the block.