Exercises

Exercises#

For these exercises, write classes to be used as decorators and make sure to provide all the functionality required. (Some exercises mention class properties. If you don’t know what they are, skip those bullet points and implement only the others.)

cache#

Write a class decorator cache that provides a cache for the function that is decorated. Assume the function decorated only accepts positional arguments that are hashable. The class decorator must provide the following functionality:

  • the attribute cache should let the user inspect the cache;

  • the attribute hits should count how many times the cache was hit (that is, values from the cache were used);

  • the attribute misses should count how many times the cache did not contain the value that was required; and

  • the method clear_cache should clear the cache and reset the attributes hits/misses.

profiler#

Write a class decorator profiler that keeps track of the time spent inside the decorated function. The class decorator must provide the following functionality:

  • the attribute calls should count how many times the function was called;

  • the attribute total_time should keep track of how much time, in total, was spent inside the function;

  • the property avg_time should return the average time spent on the function per call; and

  • the method reset should reset everything.

history#

Write a class decorator history(maxsize) that keeps track of the history of values returned by a given function. The class decorator must provide the following functionality:

  • the argument maxsize determines the maximum history size, which should never be exceeded;

  • the attribute history should let the user inspect the history as an iterable (doesn’t have to be a list);

  • the property most_recent should return the most recent return value from that function;

  • the property oldest should return the oldest item in the history; and

  • the method clear_history should clear the function history.

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