Context manager to allow getting an item from a dictionary and reusing

get_item_ctx_mgr.py

class get_item(object):
    def __init__(self, d, i):
        self.d = d
        self.i = i

    def __enter__(self):
        if self.i in self.d:
            return self.d[self.i]
        return None

And I only pasted it here to ask if there was something like this in stdlib already that I missed. (Which I'm pretty sure there isn't because it's silly.)