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[PEP 451] "target" arg of find_spec() is not exclusive to reloading.

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Eric Snow 2013-11-04 16:40:45 -07:00
parent eb0946e474
commit f96659cba7
1 changed files with 19 additions and 14 deletions
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pep-0451.txt
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@ -717,22 +717,27 @@ explicit method name aren't worth it.
The "target" parameter of find_spec() The "target" parameter of find_spec()
------------------------------------- -------------------------------------
A module object with the same name as the "name" argument (or None, the A call to find_spec() may optionally include a "target" argument. This
default) should be passed in to "exising". This argument allows the is the module object that will be used subsequently as the target of
finder to build the module spec with more information than is otherwise loading. During normal import (and by default) "target" is None,
available. This is particularly relevant in identifying the loader to meaning the target module has yet to be created. During reloading the
use. module passed in to reload() is passed through to find_spec() as the
target. This argument allows the finder to build the module spec with
more information than is otherwise available. Doing so is particularly
relevant in identifying the loader to use.
Through find_spec() the finder will always identify the loader it Through find_spec() the finder will always identify the loader it
will return in the spec. In the case of reload, at this point the will return in the spec (or return None). At the point the loader is
finder should also decide whether or not the loader supports loading identified, the finder should also decide whether or not the loader
into the module-to-be-reloaded (which was passed in to find_spec() as supports loading into the target module, in the case that "target" is
"target"). This decision may entail consulting with the loader. If passed in. This decision may entail consulting with the loader.
the finder determines that the loader does not support reloading that
module, it should either find another loader or raise ImportError If the finder determines that the loader does not support loading into
(completely stopping import of the module). This reload decision is the target module, it should either find another loader or raise
important since, as noted in `How Reloading Will Work`_, loaders will ImportError (completely stopping import of the module). This
no longer be able to trivially identify a reload situation on their own. determination is especially important during reload since, as noted in
`How Reloading Will Work`_, loaders will no longer be able to trivially
identify a reload situation on their own.
Two alternatives were presented to the "target" parameter: Two alternatives were presented to the "target" parameter:
Loader.supports_reload() and adding "target" to Loader.exec_module() Loader.supports_reload() and adding "target" to Loader.exec_module()