Lesson 6 Advanced Discussion ✅

Part 1 (2019) Advanced (Part 1 v3)
3

I guess that’s true for most cases when we’re dealing with releasable resources, like files, DB connections, etc. However, I would say that nothing actually restricts one from using context managers for different purposes. Like, for example, I am using the following class to track execution time:

import time
from timeit import default_timer


class Timer:
    """Simple util to measure execution time.

    Examples
    --------
    >>> import time
    >>> with Timer() as timer:
    ...     time.sleep(1)
    >>> print(timer)
    00:00:01
    """
    def __init__(self):
        self.start = None
        self.elapsed = None

    def __enter__(self):
        self.start = default_timer()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.elapsed = default_timer() - self.start

    def __float__(self):
        return self.elapsed

    def __str__(self):
        return self.verbose()

    def verbose(self):
        if self.elapsed is None:
            return '<not-measured>'
        return time.strftime('%H:%M:%S', time.gmtime(self.elapsed))

So, essentially, it is a context manager but it doesn’t really release any resources. I guess that similar examples could probably be found in the contextlib module. Like, stdout redirection or warnings/exceptions suppression.

In general, from my point of view, the context manager could be thought of as being an execution scope with some specific condition enforced.

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