Context managers
When working with external resources or global state, we often need to perform some cleanup steps, like releasing the resources or restoring the original state, when we are done. Failing to clean up properly could result in all manner of bugs. Therefore, we need to ensure that our cleanup code will be executed even if an exception happens. We could use try/finally statements, but this is not always convenient and could result in a lot of repetition, as we often have to perform similar cleanup steps whenever we work with a particular type of resource. Context managers solve this problem by creating an execution context in which we can work with a resource or modified state and automatically perform any necessary cleanup when we leave that context, even if an exception was raised.
One example of global state that we may want to modify temporarily is the precision for decimal computations. For example, suppose we need to perform a particular computation to a specific...
