> can be evalf'ed That's a clear and good reminder.
/c On Monday, September 13, 2021 at 12:10:50 PM UTC-5 [email protected] wrote: > 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 <[email protected]> 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 <[email protected]> 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 [email protected] > 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 [email protected]. > >>> 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 [email protected]. > > 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/69d8097b-b81b-4490-ae85-0dbb946346c1n%40googlegroups.com.
