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devel / comp.lang.python / Re: Can you help me with this memoization simple example?

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o Re: Can you help me with this memoization simple example?marc nicole

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Re: Can you help me with this memoization simple example?

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 by: marc nicole - Sun, 31 Mar 2024 08:04 UTC

Thanks for the first comment which I incorporated

but when you say "You can't use a list as a key, but you can use a tuple as
a key,
provided that the elements of the tuple are also immutable."

does it mean the result of sum of the array is not convenient to use as
key as I do?
Which tuple I should use to refer to the underlying list value as you
suggest?

Anything else is good in my code ?

Thanks

Le dim. 31 mars 2024 à 01:44, MRAB via Python-list <python-list@python..org>
a écrit :

> On 2024-03-31 00:09, marc nicole via Python-list wrote:
> > I am creating a memoization example with a function that adds up /
> averages
> > the elements of an array and compares it with the cached ones to retrieve
> > them in case they are already stored.
> >
> > In addition, I want to store only if the result of the function differs
> > considerably (passes a threshold e.g. 500000 below).
> >
> > I created an example using a decorator to do so, the results using the
> > decorator is slightly faster than without the memoization which is OK,
> but
> > is the logic of the decorator correct ? anybody can tell me ?
> >
> > My code is attached below:
> >
> >
> >
> > import time
> >
> >
> > def memoize(f):
> > cache = {}
> >
> > def g(*args):
> > if args[1] == "avg":
> > sum_key_arr = sum(list(args[0])) / len(list(args[0]))
>
> 'list' will iterate over args[0] to make a list, and 'sum' will iterate
> over that list.
>
> It would be simpler to just let 'sum' iterate over args[0].
>
> > elif args[1] == "sum":
> > sum_key_arr = sum(list(args[0]))
> > if sum_key_arr not in cache:
> > for (
> > key,
> > value,
> > ) in (
> > cache.items()
> > ): # key in dict cannot be an array so I use the sum of the
> > array as the key
>
> You can't use a list as a key, but you can use a tuple as a key,
> provided that the elements of the tuple are also immutable.
>
> > if (
> > abs(sum_key_arr - key) <= 500000
> > ): # threshold is great here so that all values are
> > approximated!
> > # print('approximated')
> > return cache[key]
> > else:
> > # print('not approximated')
> > cache[sum_key_arr] = f(args[0], args[1])
> > return cache[sum_key_arr]
> >
> > return g
> >
> >
> > @memoize
> > def aggregate(dict_list_arr, operation):
> > if operation == "avg":
> > return sum(list(dict_list_arr)) / len(list(dict_list_arr))
> > if operation == "sum":
> > return sum(list(dict_list_arr))
> > return None
> >
> >
> > t = time.time()
> > for i in range(200, 15000):
> > res = aggregate(list(range(i)), "avg")
> >
> > elapsed = time.time() - t
> > print(res)
> > print(elapsed)
>
>
> --
> https://mail.python.org/mailman/listinfo/python-list
>

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