A glossary would be a great idea.
By the way, I am going to start writing a lot of documentation in
SymPy soon (see https://groups.google.com/g/sympy/c/vYsavewGj1w). If
anyone has things in SymPy that they wish were documented better,
particularly the sorts of things that would go in high-level
explanations and how-to guides, please reach out to me. We will likely
be running some sort of survey for the same so watch this space for
more information in the coming months.
On Mon, Sep 13, 2021 at 12:14 PM Oscar Benjamin
<oscar.j.benja...@gmail.com> wrote:
>
> There is also is_Number vs is_number. There is also is_comparable which means
> can be evalf'd to a real number.
As an aside, I really wish we didn't have the is_Uppercase attributes.
They were implemented as a performance hack because attribute lookups
are slightly faster than isinstance(). But the cost they have had in
terms of user confusion greatly outweighs any performance gain they
have produced. We should consider deprecating them, or at the very
least, banning the creation of new ones on new classes. I think it's
also unfortunate that we have is_ methods that aren't actually part of
the assumptions system. But that's just something we'll just have to
document and live with.
Aaron Meurer
>
> 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 <asmeu...@gmail.com> 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 <smi...@gmail.com> 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 asme...@gmail.com 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 <distan...@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.
>> >> >>>
>> >> >>> --
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