TypeError：无法将表达式转换为使用Sympy浮动

Question

I'm trying to use sympy but am having trouble with its Symbol Objects.

import sympy as sy
from scipy import special as sp

def derivativeBMax2(s):    
x = sy.symbols('x', real=True)
B0 = 1 
H = 1
alpha = 2.4048 
B_azimuthal = B0 * H * sp.jv(1, alpha * sy.sqrt((float(x) ** 2) + (s ** 2)))

sp.jv from its documentation: https://docs.scipy.org/doc/scipy/reference/generated/scipy.special.jv.html

requires a float for its second argument and when I convert x into a float it raises

TypeError: can't convert expression to float 

I want to eventually differentiate B_azimuthal with sympy's diff()

How can I make x both a symbol and also a float for scipy's jv function?

Answer 1

If scipy requires a float there is nothing you can do (other than replace the Symbol x with a float). If you want to work with it symbollically, why not just use SymPy's besselj function in sympy/functions/special/bessel.py . The docstring of that function gives examples of using symbolic arguments and does a differentiation, too.