The varieties of `is_lowercase` don't bother me as much: some are easy to compute independently (like `is_number`) whereas others are more complicated and depend on other attributes (like `is_real`).
/c On Monday, September 13, 2021 at 1:22:38 PM UTC-5 asme...@gmail.com wrote: > 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....@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 <asme...@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. > >> >> >>> > >> >> >>> -- > >> >> >>> 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+un...@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+un...@googlegroups.com. > >> > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/69d8097b-b81b-4490-ae85-0dbb946346c1n%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+un...@googlegroups.com. > >> To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/CAKgW%3D6LOouUDFL9eooBukJz5G%2BSSMOoFWkVBLvwbqjrbduSjkA%40mail.gmail.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+un...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/CAHVvXxQeJ8eOdCpSKsiAXPjZKrd_jS2WRmfLdZS_Drjm377L5g%40mail.gmail.com > . > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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