Well...I think I have resolved that problem. I am still not totally clear
on when Sage references Sage variables vs. Python variables.
Nevertheless...heh...I'm sure I will find out.
But, I would like to restate what I was trying to achieve.
Let's say I have a need to display a Question and an Answer.
The source for the Question and Answer comes from a single string.
And suppose the string has 0 -> n sub-strings that are to be replaced with
random strings. The substituted Question string is to be
displayed, and then evaluated to derive an Answer string.
Here is my working example (after 10 attempts) to create the Question=
"2*random"
and the Answer=2*random.
*exec(compile("r=random_prime(100);Q='2*'+str(r);A=2*r
","Users/user6/TEMP.TXT","single")) *
Then Question can be set to Q
and Answer to A.
So, is there a better way to do this? I intend to perform
this task within a Python program running under SageMath.
Thank you.
On Saturday, June 19, 2021 at 6:18:50 PM UTC-7 enthor wrote:
> My objective is to concisely define an expression with variables,
> assign values to the variables, and then compute the answer.
>
> Here is what I did today:
>
> ┌────────────────────────────────────────────────────────────────────┐
> │ SageMath version 9.3.rc4, Release Date: 2021-04-18 │
> │ Using Python 3.9.2. Type "help()" for help. │
> └────────────────────────────────────────────────────────────────────┘
> ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
> ┃ Warning: this is a prerelease version, and it may be unstable. ┃
> ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
> sage: z = SR.var('z')
>
> sage: i = 2 * z
>
> sage: i
>
> 2*z
> sage: z
>
> z
> sage: type(i)
>
> <class 'sage.symbolic.expression.Expression'>
> sage: type(z)
>
> <class 'sage.symbolic.expression.Expression'>
> sage: z = random_prime(100)
>
> sage: z
>
> 79
> sage: type(z)
>
> <class 'sage.rings.integer.Integer'>
> sage: i
>
> 2*z
> sage: valuation(i)
>
> ---------------------------------------------------------------------------
> AttributeError Traceback (most recent call last)
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/arith/misc.py
>
> in valuation(m, *args, **kwds)
> 743 try:
> --> 744 return m.valuation(*args, **kwds)
> 745 except AttributeError:
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/element.pyx
>
> in sage.structure.element.Element.__getattr__
> (build/cythonized/sage/structure/element.c:4709)()
> 492 """
> --> 493 return self.getattr_from_category(name)
> 494
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/element.pyx
>
> in sage.structure.element.Element.getattr_from_category
> (build/cythonized/sage/structure/element.c:4821)()
> 505 cls = P._abstract_element_class
> --> 506 return getattr_from_other_class(self, cls, name)
> 507
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/cpython/getattr.pyx
>
> in sage.cpython.getattr.getattr_from_other_class
> (build/cythonized/sage/cpython/getattr.c:2619)()
> 371 dummy_error_message.name = name
> --> 372 raise AttributeError(dummy_error_message)
> 373 attribute = <object>attr
>
> AttributeError: 'sage.symbolic.expression.Expression' object has no
> attribute '__custom_name'
>
> During handling of the above exception, another exception occurred:
>
> TypeError Traceback (most recent call last)
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/symbolic/expression.pyx
>
> in sage.symbolic.expression.Expression._integer_
> (build/cythonized/sage/symbolic/expression.cpp:8808)()
> 1298 try:
> -> 1299 n = self.pyobject()
> 1300 except TypeError:
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/symbolic/expression.pyx
>
> in sage.symbolic.expression.Expression.pyobject
> (build/cythonized/sage/symbolic/expression.cpp:6143)()
> 586 if not is_a_numeric(self._gobj):
> --> 587 raise TypeError("self must be a numeric expression")
> 588 return py_object_from_numeric(self._gobj)
>
> TypeError: self must be a numeric expression
>
> During handling of the above exception, another exception occurred:
>
> TypeError Traceback (most recent call last)
> <ipython-input-11-227398a9d1bf> in <module>
> ----> 1 valuation(i)
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/arith/misc.py
>
> in valuation(m, *args, **kwds)
> 744 return m.valuation(*args, **kwds)
> 745 except AttributeError:
> --> 746 return ZZ(m).valuation(*args, **kwds)
> 747
> 748
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/parent.pyx
>
> in sage.structure.parent.Parent.__call__
> (build/cythonized/sage/structure/parent.c:9335)()
> 896 if mor is not None:
> 897 if no_extra_args:
> --> 898 return mor._call_(x)
> 899 else:
> 900 return mor._call_with_args(x, args, kwds)
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/structure/coerce_maps.pyx
>
> in sage.structure.coerce_maps.NamedConvertMap._call_
> (build/cythonized/sage/structure/coerce_maps.c:6042)()
> 285 raise TypeError("Cannot coerce {} to {}".format(x, C))
> 286 cdef Map m
> --> 287 cdef Element e = method(C)
> 288 if e is None:
> 289 raise RuntimeError("BUG in coercion model: {} method
> of {} returned None".format(self.method_name, type(x)))
>
> /var/tmp/sage-9.3.rc4-current/local/lib/python3.9/site-packages/sage/symbolic/expression.pyx
>
> in sage.symbolic.expression.Expression._integer_
> (build/cythonized/sage/symbolic/expression.cpp:8857)()
> 1299 n = self.pyobject()
> 1300 except TypeError:
> -> 1301 raise TypeError("unable to convert %r to an integer" %
> self)
> 1302 if isinstance(n, sage.rings.integer.Integer):
> 1303 return n
>
> TypeError: unable to convert 2*z to an integer
> sage:
>
>
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