Miscellaneous utilities¶
-
class
sage.structure.misc.
AttributeErrorMessage
¶ Bases:
object
Tries to emulate the standard Python
AttributeError
message.Note
The typical fate of an attribute error is being caught. Hence, under normal circumstances, nobody will ever see the error message. The idea for this class is to provide an object that is fast to create and whose string representation is an attribute error’s message. That string representation is only created if someone wants to see it.
EXAMPLES:
sage: 1.bla #indirect doctest Traceback (most recent call last): ... AttributeError: 'sage.rings.integer.Integer' object has no attribute 'bla' sage: QQ[x].gen().bla Traceback (most recent call last): ... AttributeError: 'sage.rings.polynomial.polynomial_rational_flint.Polynomial_rational_flint' object has no attribute 'bla' sage: from sage.structure.misc import AttributeErrorMessage sage: AttributeErrorMessage(int(1),'bla') 'int' object has no attribute 'bla'
TESTS:
By trac ticket #14100, the attribute errors raised on elements and parents are unique objects. The error message of this unique error object is changed inplace. This is for reasons of efficiency.
sage: try: ....: 1.__bla ....: except AttributeError as ElementError: ....: pass sage: ElementError AttributeError('sage.rings.integer.Integer' object has no attribute '__bla',) sage: try: ....: x.__bla ....: except AttributeError as ElementError2: ....: pass sage: ElementError2 is ElementError True sage: ElementError AttributeError('sage.symbolic.expression.Expression' object has no attribute '__bla',) sage: isinstance(ElementError.args[0], sage.structure.misc.AttributeErrorMessage) True
Hence, if one really needs the error message as a string, then one should make a copy of its string representation before it changes. Attribute Errors of parents behave similarly:
sage: try: ....: QQ.__bla ....: except AttributeError as ParentError: ....: pass sage: ParentError AttributeError('RationalField_with_category' object has no attribute '__bla',) sage: try: ....: ZZ.__bla ....: except AttributeError as ParentError2: ....: pass sage: ParentError2 is ParentError True sage: ParentError2 AttributeError('sage.rings.integer_ring.IntegerRing_class' object has no attribute '__bla',) sage: ParentError2 is ElementError True
AUTHOR:
- Simon King (2011-05-21)
-
cls
¶
-
name
¶
-
sage.structure.misc.
dir_with_other_class
(self, cls)¶ Emulates
dir(self)
, as if self was also an instancecls
, right aftercaller_class
in the method resolution order (self.__class__.mro()
)EXAMPLES:
sage: class A(object): ....: a = 1 ....: b = 2 ....: c = 3 sage: class B(object): ....: b = 2 ....: c = 3 ....: d = 4 sage: x = A() sage: x.c = 1; x.e = 1 sage: from sage.structure.misc import dir_with_other_class sage: dir_with_other_class(x, B) [..., 'a', 'b', 'c', 'd', 'e']
Check that objects without dicts are well handled:
sage: cython("cdef class A:\n cdef public int a") sage: cython("cdef class B:\n cdef public int b") sage: x = A() sage: x.a = 1 sage: hasattr(x,'__dict__') False sage: dir_with_other_class(x, B) [..., 'a', 'b']
TESTS:
Check that trac ticket #13043 is fixed:
sage: len(dir(RIF))==len(set(dir(RIF))) True
-
sage.structure.misc.
getattr_from_other_class
(self, cls, name)¶ Emulate
getattr(self, name)
, as ifself
was an instance ofcls
.INPUT:
self
– some objectcls
– a new-style classname
– a string
If self is an instance of cls, raises an
AttributeError
, to avoid a double lookup. This function is intended to be called from __getattr__, and so should not be called if name is an attribute of self.EXAMPLES:
sage: from sage.structure.misc import getattr_from_other_class sage: class A(object): ....: def inc(self): ....: return self + 1 ....: ....: @staticmethod ....: def greeting(): ....: print("Hello World!") ....: ....: @lazy_attribute ....: def lazy_attribute(self): ....: return repr(self) sage: getattr_from_other_class(1, A, "inc") <bound method A.inc of 1> sage: getattr_from_other_class(1, A, "inc")() 2
Static methods work:
sage: getattr_from_other_class(1, A, "greeting")() Hello World!
Caveat: lazy attributes work with extension types only if they allow attribute assignment or have a public attribute
__cached_methods
of type<dict>
. This condition is satisfied, e.g., by any class that is derived fromParent
:sage: getattr_from_other_class(1, A, "lazy_attribute") Traceback (most recent call last): ... AttributeError: 'sage.rings.integer.Integer' object has no attribute 'lazy_attribute'
The integer ring is a parent, so, lazy attributes work:
sage: getattr_from_other_class(ZZ, A, "lazy_attribute") 'Integer Ring' sage: getattr_from_other_class(PolynomialRing(QQ, name='x', sparse=True).one(), A, "lazy_attribute") '1' sage: getattr_from_other_class(PolynomialRing(QQ, name='x', implementation="FLINT").one(), A, "lazy_attribute") Traceback (most recent call last): ... AttributeError: 'sage.rings.polynomial.polynomial_rational_flint.Polynomial_rational_flint' object has no attribute 'lazy_attribute'
In general, descriptors are not yet well supported, because they often do not accept to be cheated with the type of their instance:
sage: A.__weakref__.__get__(1) Traceback (most recent call last): ... TypeError: descriptor '__weakref__' for 'A' objects doesn't apply to 'sage.rings.integer.Integer' object
When this occurs, an
AttributeError
is raised:sage: getattr_from_other_class(1, A, "__weakref__") Traceback (most recent call last): ... AttributeError: 'sage.rings.integer.Integer' object has no attribute '__weakref__'
This was caught by trac ticket #8296 for which we do a couple more tests:
sage: "__weakref__" in dir(A) True sage: "__weakref__" in dir(1) True sage: 1.__weakref__ Traceback (most recent call last): ... AttributeError: 'sage.rings.integer.Integer' object has no attribute '__weakref__' sage: n = 1 sage: ip = get_ipython() # not tested: only works in interactive shell sage: ip.magic_psearch('n.N') # not tested: only works in interactive shell n.N sage: ip.magic_psearch('n.__weakref__') # not tested: only works in interactive shell
Caveat: When __call__ is not defined for instances, using
A.__call__
yields the method__call__
of the class. We use a workaround but there is no guarantee for robustness.sage: getattr_from_other_class(1, A, “__call__”) Traceback (most recent call last): ... AttributeError: ‘sage.rings.integer.Integer’ object has no attribute ‘__call__’TESTS:
Check that we do not pick up special attributes from the
type
class, see trac ticket #20686:sage: getattr_from_other_class(1, type, "__name__") Traceback (most recent call last): ... AttributeError: 'sage.rings.integer.Integer' object has no attribute '__name__'
This does not work with an old-style class:
sage: class OldStyle: ....: pass sage: getattr_from_other_class(1, OldStyle, "foo") Traceback (most recent call last): ... TypeError: <class __main__.OldStyle at ...> is not a type
Non-strings as “name” are handled gracefully:
sage: getattr_from_other_class(1, type, None) Traceback (most recent call last): ... AttributeError: 'sage.rings.integer.Integer' object has no attribute None
-
sage.structure.misc.
is_extension_type
(cls)¶ INPUT:
- cls: a class
Tests whether cls is an extension type (int, list, cython compiled classes, ...)
EXAMPLES:
sage: from sage.structure.parent import is_extension_type sage: is_extension_type(int) True sage: is_extension_type(list) True sage: is_extension_type(ZZ.__class__) True sage: is_extension_type(QQ.__class__) False