Hi David,
You could write a simple converter to convert all ints to sympy Integers
if you are writing the code inside a function. See code below.
Isuru
import sympy
from sympy.interactive.session import int_to_Integer
import inspect
import types
def use_sympy_ints(f):
# https://stackoverflow.com/q/57480368/4768820
source = inspect.getsource(f)
source = '\n'.join(source.splitlines()[1:]) # remove the decorator
first line.
old_code_obj = f.__code__
new_ast= int_to_Integer(source)
new_code_obj = compile(new_ast, old_code_obj.co_filename, 'exec')
g = dict(f.__globals__)
g['Integer'] = sympy.Integer
new_f = types.FunctionType(new_code_obj.co_consts[0], g)
return new_f
@use_sympy_ints
def foo(x):
return x + 1 / 2
On Fri, Jul 7, 2023 at 3:32 AM Aaron Meurer <asmeu...@gmail.com> wrote:
> On Thu, Jul 6, 2023 at 4:15 PM David Bailey <d...@dbailey.co.uk> wrote:
> >
> > On 05/07/2023 21:40, Aaron Meurer wrote:
> > > For interactive use, just passing a string to S() (or equivalently
> > > sympify() or parse_expr()) is the simplest way to deal with this.
> > > However, I would avoid this for non-interactive usage (i.e., any code
> > > that gets saved to be executed later). Putting your expression in a
> > > string breaks the ability for Python to parse it directly, meaning
> > > things like simple syntax errors won't be caught until the code gets
> > > run.
> > >
> > > You should also be very careful when doing this if you use
> > > assumptions. S("x + 1") will create a symbol x with the default
> > > assumptions. If you already defined x with assumptions, like
> > >
> > > x = symbols('x', real=True)
> > >
> > > then this will be a *different* symbol. For example:
> >
> > Thanks for that caution, Aaron,
> >
> > This whole problem reminds me vaguely of a friend of mine that bought an
> > early Sinclair calculator. He discovered that ln(2) was seriously
> > inaccurate, so he wrote to them. They replied that there was nothing
> > wrong with his calculator, he had just chosen an unfortunate example!
> >
> > What I'm trying to say is that there must be people out there who gave
> > given up on SymPy after discovering what it does to 1/2*x, or worse
> > still, got an error in their work (particularly if using Python 2).
>
> No one should be using Python 2 at this point. So fortunately that
> particular headache is behind us.
>
> >
> > Thinking about it, I can see how hard it is to do something really
> > effective about this problem, but couldn't you prevail on the Python
> > term to insert a hook in the Python parser to make it possible to change
> > an input string before Python parses it and applies its integer division
> > rule?
>
> That particular way of solving the problem would very likely be
> rejected. It's basically equivalent to adding macros to the language,
> which has been rejected multiple times before.
>
> I have wondered if it wouldn't be possible for Python to keep track of
> how purely numeric constants are created at compile time and store
> that information on the constant. Since it would only apply to pure
> numbers and would only happen at compile time, it would have basically
> no runtime penalties. That would also allow something like
> 1.0000000000000000001, which automatically truncates to 1.0, to create
> sympy.Float('1.0000000000000000001'). But it's only a vague idea I've
> ruminated on and I haven't written to the core Python team about it.
>
> Aaron Meurer
>
> >
> > David
> >
> > --
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