There is also is_Number vs is_number. There is also is_comparable which
means can be evalf'd to a real number.
There should be a glossary of all the different attributes that are used
throughout sympy:
In [*1*]: *for* name *in* dir(x):
...: *if* name.startswith('is'):
...: print(name)
...:
is_Add
is_AlgebraicNumber
is_Atom
is_Boolean
is_Derivative
is_Dummy
is_Equality
is_Float
is_Function
is_Indexed
is_Integer
is_MatAdd
is_MatMul
is_Matrix
is_Mul
is_Not
is_Number
is_NumberSymbol
is_Order
is_Piecewise
is_Point
is_Poly
is_Pow
is_Rational
is_Relational
is_Symbol
is_Vector
is_Wild
is_algebraic
is_algebraic_expr
is_antihermitian
is_commutative
is_comparable
is_complex
is_composite
is_constant
is_even
is_extended_negative
is_extended_nonnegative
is_extended_nonpositive
is_extended_nonzero
is_extended_positive
is_extended_real
is_finite
is_hermitian
is_hypergeometric
is_imaginary
is_infinite
is_integer
is_irrational
is_meromorphic
is_negative
is_noninteger
is_nonnegative
is_nonpositive
is_nonzero
is_number
is_odd
is_polar
is_polynomial
is_positive
is_prime
is_rational
is_rational_function
is_real
is_scalar
is_symbol
is_transcendental
is_zero
On Mon, 13 Sept 2021 at 18:56, Aaron Meurer <[email protected]> wrote:
> This would be a good thing to have some standalone documentation on.
> There are also some related things like the functionality that is used
> by diff() to determine what can be used as a differentiation variable,
> which is a little more complex than just free_symbols in general
> because you can have things like derivatives with respect to indexed
> expressions.
>
> Aaron Meurer
>
> On Mon, Sep 13, 2021 at 11:48 AM Chris Smith <[email protected]> wrote:
> >
> > > 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.
> >> >>>
> >> >>> --
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