Hi!
On 2012-05-02, P Purkayastha <ppu...@gmail.com> wrote:
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> Is there a way to use lazy_attribute in cython code?
lazy_attribute requires that the object allows attributes to be set.
Thus, it works if you have a non-cdef class (even if the class is
defined in Cython), but I guess you'd need to implement getattr/setattr
support for a cdef class before being able to use it.
Example:
sage: cython("""
....: from sage.misc.lazy_attribute import lazy_attribute
....: class A:
....: @lazy_attribute
....: def a(self):
....: return "A"
....: cdef class B:
....: @lazy_attribute
....: def b(self):
....: return "B"
....: """)
sage: a = A()
sage: b = B()
sage: a.a
'A'
sage: b.b
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
...
AttributeError: '_home_simon__sage_temp_linux_sqwp_site_5210_tmp_0_' object
attribute 'b' is read-only
Background: When a lazy attribute L is requested first for an object O, then
L is looked up in O.__class__. It has a __get__ method to bind it to O,
and the __get__ method overrides L in O. Hence, we need that
setattr(O,'L',some_value) works (which doesn't, in the example above).
Best regards,
Simon
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