#14187: Check that lazy imports are not resolved during startup
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Reporter: vbraun | Owner: tbd
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.8
Component: performance | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers: Nicolas M. Thiéry
Authors: Volker Braun | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
Replying to [comment:17 vbraun]:
> I disagree, imports are much more legible without the lazy_import call.
Would we even have a hook to do this? The problem is that `lazy_import`
must register the `globals` dictionary in which to change the binding. It
can do that when `lazy_import` gets called explicitly, because `globals()`
gives you the appropriate dictionary then.
When you do `from all import NN`, you get that `blah.NN` gets bound to the
then current binding of `all.NN`, which is a `LazyImport` object. I don't
think that at any point that `LazyImport` object gets notified that it is
getting bound to an entry in a different `globals` dictionary, though. So
how would `LazyImport` even know which other dictionaries to mess with in
order to resolve the lazy loading? You'd have to reach quite deep into
Python's import mechanism.
The "hack-free" solution is to avoid `from ... import` and, in time
critical pieces of code, load "all.NN" into a local variable at runtime
(which is faster anyway). Of course, that doesn't solve the readability
problem ...
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14187#comment:19>
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