在 SymPy 中计算总和

Question

I want to evaluate the sum

using Python and SymPy, I'm relatively new using SymPy and the first thing I tried was

from sympy import exp, oo, summation, symbols

n, x = symbols('n,x')
summation(exp(-n*x), (n, 1, oo))

But it doesn't work, it just returns the unevaluated sum. I can make it work using

from sympy import exp, oo, summation, symbols

n, x = symbols('n,x')
f = exp(-x)
summation(x**(-n), (n, 1, oo)).subs(x,f)

But I would like to know if it is possible to make it work without need to break the expression into x^n and then substitute x by e^-x.

Thank you

Answer 1

Try using the following:

x , n = smp.symbols('x n')
smp.Sum(smp.exp(-n*x),(n, 1, smp.oo))