[Python-ideas] Delayed Execution via Keyword

[Pavol Lisy]

On 2/18/17, Steven D'Aprano <steve at pearwood.info> wrote:

Sorry Steve that I use your words probably too much out of context!

I just want to reuse your examples to analyze if proposed "delayed
execution" is really necessary. Thanks for them! :)

> print("Start")
> result = delayed: get_nth_prime(10**6)  # I dislike this syntax
> print("Done")
> print(result)

If we change "delayed" keyword to "lambda" keyword then we just need
to explicitly say when to evaluate (which I am not sure is bad thing).

On 2/18/17, Steven D'Aprano <steve at pearwood.info> wrote:

> The caching means that:
> spam  = delayed: calculate(1)
> eggs = spam
>
> eggs == spam would be true, and calculate would have only been called once,
> not twice.

If we really need something like this then we could use "def" keyword
(for delayed execution) and explicitely caching (for example with
functools.lru_cache).

print("Start")
@functools.lru_cache(1)
def result():
    return get_nth_prime(10**6)   # this code is delayed
print("Done")
print(result())
print("Start 2")
print(result())
result2 = result
print(result() == result2())
print("Done 2")