Hi Ranier,
Here's a way to do it:
>>> import sympy
>>> x, y, z = sympy.symbols('x y z')
>>> sympy.solvers.inequalities.reduce_inequalities([x + 2 > 0, x < 5], x)
(-2 < x) & (x < 5)
reduce_inequalities is the top-level inequality reducer, which will call
other lower-level functions (such as reduce_rational_inequalities) as
needed. reduce_inequalities takes a simple list, rather than a nested list,
of inequalities.
I'm actually drafting a guide page on this topic now; glad to know it's of
interest! You can access the draft
<https://output.circle-artifacts.com/output/job/a1f8297d-6be8-4627-9f47-a969709f9293/artifacts/0/doc/_build/html/guides/solving/solve-system-of-inequalities-algebraically.html>,
and I'd appreciate any feedback (either here or on the pull request
<https://github.com/sympy/sympy/pull/23768> on GitHub).
Best,
Jeremy
P.S. If you like, you can use less-verbose function calls by importing
reduce_inequalities and symbols from SymPy:
>>> from sympy import reduce_inequalities, symbols
>>> x, y, z = symbols('x y z')
>>> reduce_inequalities([x + 2 > 0, x < 5], x)
(-2 < x) & (x < 5)
On Sat, Aug 6, 2022 at 3:31 AM 'Rainer Dorsch' via sympy <
sympy@googlegroups.com> wrote:
> Hi,
>
> I just started with sympy, and try to understand how to tell sympy, what I
> want. I tried
> print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 >
> 0],[x
> < 5]], x))
> and expected
> (-2 < x) & (x < 5)
> but got
> (-oo < x) & (x < oo)
> Can anybody tell how I can tell sympy that x should satisfy both
> inequalities
> the same time?
> For me it seems sympy rather interprets the set of equations rather as an
> "or"
> and not an "and"
>
> Here is the full example
>
> rd@h370:~/tmp.nobackup$ cat test-sympy.py
> import sympy
>
> x, y, z = sympy.symbols('x y z')
> sympy.init_printing(use_unicode=True)
>
> print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 >
> 0]],
> x))
>
>
> print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 >
> 0],[x
> < 5]], x))
> rd@h370:~/tmp.nobackup$ python3 test-sympy.py
> (-2 < x) & (x < oo)
> (-oo < x) & (x < oo)
> rd@h370:~/tmp.nobackup$
>
>
> Any hint is welcome.
>
> Thanks
> Rainer
>
>
> --
> Rainer Dorsch
> http://bokomoko.de/
>
>
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