Context managers may end up being almost as important as the subroutine itself. We’ve only scratched the surface with them. […] Basic has a
withstatement, there are
withstatements in lots of languages. But they don’t do the same thing, they all do something very shallow, they save you from repeated dotted [attribute] lookups, they don’t do setup and tear down. Just because it’s the same name don’t think it’s the same thing. The
withstatement is a very big deal.
— Raymond Hettinger Eloquent Python evangelist
In this chapter, we will discuss control flow features that are not so common in other languages, and for this reason tend to be overlooked or underused in Python. They are:
withstatement and context managers
with statement sets up a temporary context and reliably tears it down, under the control of a context manager object. This prevents errors and reduces boilerplate code, making APIs at the same time safer and easier to use. Python programmers are finding lots of uses for
with blocks beyond automatic file closing.
else clause is completely unrelated to
with. But this is Part V, and I couldn’t find another place for covering
else, and I wouldn’t have a one-page chapter about it, so here it is.
Let’s review the smaller topic to get to the real substance of this chapter.
This is no secret, but it is an underappreciated language ...