Thanks! This does exaclty what I wanted. Now, for the question, should I be embarassed for not finding it myself. This is in fact documented in https://docs.sympy.org/latest/modules/printing.html It looks like all of my searching was for reversing the order of an expression, which is hard, but reversing the order or printing is easy.
On Tuesday, February 13, 2024 at 12:46:43 AM UTC+1 [email protected] wrote: > The order in printing can be controlled with the order flag to the > printer. Using latex(expr, order='rev-lex') will cause polynomials to > print in reverse lexicographic order, which is the order you want. > > It's not a good idea to use evaluate=False to try to control printing > behavior, as this can break other things. Instead, you should use the > existing flags in the printer in question, or customize the printer > with a subclass if the built-in behavior doesn't meet your needs. > > Aaron Meurer > > On Sat, Feb 10, 2024 at 1:58 PM Thomas Ligon <[email protected]> wrote: > > > > I am trying to reverse the order of an expression before printing it for > my documentation, and I want ascending order, but SymPy always gives me > descending order. All of the expressions are polynomials, specifically > partial sums of power series. Since, according to Internet searches, there > is no easy way to do this, I have tried a number of things, including > manipulating the expression tree. The original expression is always Add of > a tuple, and each tuple is a rational number and x**n. When I loop through > the expression and Add the components, I always get the same order. The > elegant solution would be to reverse the tuple and Add it all at once, but > that is deprecated and gives me a tuple instead of a sum. > > > > Here is some sample code, a test program that demonstrates the problem. > > > > from sympy import symbols, Rational, Add, latex, Eq > > x = symbols('x') > > lhs = symbols('X') > > rhs = Rational(3)/Rational(4)*x**3 + Rational(2)/Rational(5)*x**2 + > Rational(1)/Rational(4)*x > > X1 = rhs.args > > #X2 = X1[::-1] # Why don't I need this? My debugger shows the expression > and the tuple in reverse order. > > X2 = X1 > > # Try the expected order of Add. This produces a sum, but with an extra > set of parantheses, and not the desired order. > > X3 = X2[0] > > X2R = X2[1:len(X2)] > > for indT in range(0, len(X2R)): > > termT = X2R[indT] > > X3 = Add(X3, termT, evaluate=False) > > # Try the other order of Add. This looks the same as X3. > > X4 = X2[0] > > for indT in range(0, len(X2R)): > > termT = X2R[indT] > > X4 = Add(termT, X4, evaluate=False) > > # Try single step. This is deprecated, gives the correct order, but > returns a tuple instead of a sum. > > #X2 = X1[::-1] # Why don't I need this? > > X2 = X1 > > X5 = Add(X2, evaluate=False) > > > > print(latex(Eq(lhs, rhs))) # original order > > print(latex(Eq(lhs, X3))) # still original order > > print(latex(Eq(lhs, X4))) # still original order > > print(latex(Eq(lhs, X5))) # desired order, but tuple instead of sum > > > > -- > > 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/166a5149-26b2-47f7-9956-943b9d379d92n%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/92fc1ab4-81bb-491c-a538-b5422e81e9dbn%40googlegroups.com.
