# PEP 517 Backend bootstrapping

**URL:** <https://discuss.python.org/t/pep-517-backend-bootstrapping/789>\
**Category:** Packaging\
**Created:** [January 30, 2019, 1:19am UTC](https://discuss.python.org/t/pep-517-backend-bootstrapping/789 "2019-01-30T01:19:16Z")\
**Posts on this page:** 1\
**Showing post:** 182

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**Author:** ![cjerdonek](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cjerdonek/32/63_2.png) [@cjerdonek](https://discuss.python.org/u/cjerdonek)\
**Post date:** [February 17, 2019, 6:00am UTC](https://discuss.python.org/t/pep-517-backend-bootstrapping/789/182 "2019-02-17T06:00:51Z")

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> [@steve.dower](#):
>
> Then you’ll need another option for “build the packages and dependencies I requested from source, but don’t bother building setuptools from source yet again” anyway.

This could be another use case to add to the list in @takluyver’s new [“Pip options for controlling use of prebuilt packages”](https://discuss.python.org/t/pip-options-for-controlling-use-of-prebuilt-packages/905) thread.

The simplest API might wind up being one that lets the user opt in or out individual packages or types of packages, in which case this would be a special case.

Also, another thing to consider is whether we could let pip re-use from previous invocations dependencies previously built from source. I’m not sure how easy or hard that would be to implement or if it would violate some other assumption.

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