Generating list of strings, need to limit both the list length and the total length of strings (without filter?)

[Štěpán Balážik]

Hi,

I'm trying to write a strategy that generates lists of strings of limited length where the sum of lengths is also limited. So far I came up with this:

from hypothesis.strategies import lists, text

LIMIT = 100

lists(text(max_size=20), max_size=20).filter(lambda strings: sum(len(s) for s in strings) < LIMIT)

This works but I suppose that I am getting a performance hit from using the filter.

Is there an obvious (or even less obvious) way to do it without the filter?

Thanks for any help you can provide.

Štěpán

[Zac Hatfield Dodds]

Hi Štěpán,

You could also express this with a .map(), taking the longest acceptable prefix of the generated list.  For example:

from hypothesis.strategies import lists, text
LIMIT = 100

def trim(ls):

    while sum(len(s) for s in strings) > LIMIT:

        ls = ls[:-1]
    return ls

lists(text(max_size=20), max_size=20).map(trim)

I'd also suggest asking such questions on https://stackoverflow.com/questions/tagged/python-hypothesis - more people are around to answer, and the answers are more likely to be found by others who have similar questions :-)

Best,

Zac

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