#10963: More functorial constructions
-------------------------------------+-------------------------------------
Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.1
Component: categories | Resolution:
Keywords: days54 | Merged in:
Authors: Nicolas M. Thiéry | Reviewers: Simon King, Frédéric
Report Upstream: N/A | Chapoton
Branch: | Work issues:
public/ticket/10963 | Commit:
Dependencies: #11224, #8327, | dbb17b11bb9e8f94b5d9d3424cd34c5efc82564c
#10193, #12895, #14516, #14722, | Stopgaps:
#13589, #14471, #15069, #15094, |
#11688, #13394, #15150, #15506 |
-------------------------------------+-------------------------------------
Comment (by nbruin):
I have to think about your explanation. I have a hunch there's a problem
with it but as long as I cannot point it out explicitly I cannot really
object.
Independently, the lazy import indeed doesn't seem to clear properly, as
was indicated by the tracebacks above already. With
{{{#!diff
diff --git a/src/sage/misc/lazy_import.pyx b/src/sage/misc/lazy_import.pyx
index 051a99b..2b96582 100644
--- a/src/sage/misc/lazy_import.pyx
+++ b/src/sage/misc/lazy_import.pyx
@@ -480,6 +480,7 @@ cdef class LazyImport(object):
documentation of :meth:`_get_object` for an explanation of
this.
"""
+ print "lazy_import.__get__(%s,%s,%s)"%(self, instance, owner)
obj = self._get_object(owner=owner)
if hasattr(obj, "__get__"):
return obj.__get__(instance, owner)
}}}
I get:
{{{
sage: Algebras(GF(13))
lazy_import.__get__(<class
'sage.categories.associative_algebras.AssociativeAlgebras'>,None,<class
'sage.categories.magmatic_algebras.MagmaticAlgebras_with_category'>)
lazy_import.__get__(<class
'sage.categories.algebras.Algebras'>,None,<class
'sage.categories.associative_algebras.AssociativeAlgebras_with_category'>)
lazy_import.__get__(<class
'sage.categories.unital_algebras.UnitalAlgebras'>,None,<class
'sage.categories.magmatic_algebras.MagmaticAlgebras_with_category'>)
Category of algebras over Finite Field of size 13
sage: Algebras(GF(5))
lazy_import.__get__(<class
'sage.categories.associative_algebras.AssociativeAlgebras'>,None,<class
'sage.categories.magmatic_algebras.MagmaticAlgebras_with_category'>)
lazy_import.__get__(<class
'sage.categories.algebras.Algebras'>,None,<class
'sage.categories.associative_algebras.AssociativeAlgebras_with_category'>)
lazy_import.__get__(<class
'sage.categories.unital_algebras.UnitalAlgebras'>,None,<class
'sage.categories.magmatic_algebras.MagmaticAlgebras_with_category'>)
Category of algebras over Finite Field of size 5
sage: Algebras(GF(7))
lazy_import.__get__(<class
'sage.categories.associative_algebras.AssociativeAlgebras'>,None,<class
'sage.categories.magmatic_algebras.MagmaticAlgebras_with_category'>)
lazy_import.__get__(<class
'sage.categories.algebras.Algebras'>,None,<class
'sage.categories.associative_algebras.AssociativeAlgebras_with_category'>)
lazy_import.__get__(<class
'sage.categories.unital_algebras.UnitalAlgebras'>,None,<class
'sage.categories.magmatic_algebras.MagmaticAlgebras_with_category'>)
Category of algebras over Finite Field of size 7
}}}
After the first call, all the lazy importing should have happened already,
so subsequent invocations shouldn't have a lazy_import in between any
more. I suspect that this happens because there is a lazy import object
somewhere that doesn't get replaced by the reference to the actual object
once it gets loaded. This is a known issue: lazy_importing objects from
modules doesn't actually work very well (lazy importing modules and then
referring to an object in the module works better, if I'm not mistaken).
So, you should probably not use lazy import for this but rather do it
manually: just keep the string first and do an actual import, replacing
the string, once you really need the object.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:340>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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