[Distutils] How to implement ‘setup.py’ functionality that itself needs third-party distributions

[Donald Stufft]

> On Jan 20, 2015, at 10:27 PM, Ben Finney <ben+python at benfinney.id.au> wrote:
> 
> Carl Meyer <carl at oddbird.net> writes:
> 
>> On 01/20/2015 07:28 PM, Ben Finney wrote:
>>> What I need is a way to express “ensure Docutils is installed before
>>> continuing with other Setuptools actions” in ‘setup.py’. I don't
>>> know of a neat way to tell Setuptools that.
>> 
>> That is the precise purpose of the `setup_requires` kwarg.
> 
> That's too late though. What I need is to be able to instruct the build
> process to install Docutils so I can get stuff done *before ‘setup()’ is
> called*.
> 
> Is there an API within Distutils or Setuptools that allows me to say “I
> haven't declared anything yet but go get and install distribution FOO
> right now”? I could do that before importing the module which needs
> Docutils.
> 

You could also add setup_requires=[“docutils”], and then pass in a
Distclass (defined in your setup.py) and/or custom cmdclass entries
which delay the import until the body of the methods on those
classes. This should be after the setup_requires code has ran so
the docutils import should work.

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Donald Stufft
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