is_number means "can be evalf'ed". So for example, we have the following
>>> f = Function('f') >>> f(0).is_number False >>> f(0).free_symbols set() So you should use is_number specifically if you are checking if you can evaluate the expression to a literal number. Aaron Meurer On Mon, Sep 13, 2021 at 10:21 AM Paul Royik <distantjob...@gmail.com> wrote: > > Thanks to everybody! > > On Monday, September 13, 2021 at 3:56:47 PM UTC+3 Oscar wrote: >> >> Think about things that are literally not numbers: >> >> In [9]: Interval(1, 2).is_number >> Out[9]: False >> >> In [10]: ImmutableMatrix([[1, 2], [3, 4]]).is_number >> Out[10]: False >> >> >> On Mon, 13 Sept 2021 at 13:00, Chris Smith <smi...@gmail.com> wrote: >>> >>> To confirm, if you mean that it is free from any Symbol (free or bound) >>> then `not expr.has(Symbol)` will be best. But if you consider `Integral(x, >>> (x, 1, 2))` as a number then you should use `is_number` or `free_symbols`, >>> with `expr.is_number` failing sooner than `not expr.free_symbols` if the >>> expression has a free symbol. (So if you suspect the expression has free >>> symbols then use `is_number`, else `free_symbols`). >>> >>> `f.is_number != (not bool(f.free_symbols))` should be an invariant for >>> Expr, but SymPy also deals with Booleans, so `S.true.is_number` is False >>> and `S.true.free_symbols` is empty. >>> >>> /c >>> >>> On Sunday, September 12, 2021 at 11:56:23 PM UTC-5 distan...@gmail.com >>> wrote: >>>> >>>> Are there any cases when f.is_number != (not bool(f.free_symbols))? >>>> >>>> If I have an arbitrary expression, what is the correct way to check >>>> whether it has variables? >>>> >>>> Thank you. >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "sympy" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to sympy+un...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/sympy/9af46205-ce22-494c-a604-c27b6682fa96n%40googlegroups.com. > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/8717be3c-0286-4741-900c-94e21573f3c5n%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6JPWqzeaC16GTx%2BaaLrxKDHdjz5qYW6dKASffZBVTmeLw%40mail.gmail.com.