调试 TypeError：只能将列表（不是“浮动”）连接到列表

Question

嘿，我正在寻求调试此代码的帮助，我使用积分方法求解 xdot 中列出的 5 个方程。 但是，我在 HIVmodel function 中的 xdot = np.array 行中不断出现错误

def HIVmodel (x, params):

r = params["r"]
  betaC = params["betaC"]
  sT = params["sT"]
  A = params["A"]
  a0 = params["a0"]
  betaV = params["betaV"]
  B = params["B"]
  alphaS = params["alphaS"]
  h = params["h"]
  sC = params["sC"]
  k = params["k"]
  alphaV = params["alphaV"]
  alphaE = params["alphaE"]
  alphaI = params["alphaI"]
  p = params["p"]
  alphaC = params["alphaC"]
  a1 = params["a1"]
  N = params["N"]


xdot = np.array([sT + (r * x[0] * x[4]) / x([4] + A) - (betaC * x[4] * x[0]) / (1 + a0 * x[3]) - (k * x[4] * x[0]) / (x[0] + B) - alphaS * x[0], (betaC * x[4] * x[0]) / (1 + a0 * x[3]) - betaV * x[1] - alphaE * x[1],
                   betaV * x[1] - h * x[2] * x[3] - alphaI * x[2], sC + p * x[3] * Ts * x[3] - alphaC * x[3],(N * alphaI * x[2]) / (1 + a1 * x[3]) - alphaV * x[4]])
  return xdot

def RungeKuttaOrder4(f, x0, t0, tf, dt):
   
  t=np.arange(t0,tf,dt)
  nt = t.size
  nx = x0.size
  x= np.zeros((nx,nt))
  x[:,0] = x0

  for k in range(nt-1):
k1 = dt * f(t[k], x[:,k])
k2 = dt * f(t[k]+dt/2, x[:,k] +k1/2)
k3 = dt * f(t[k]+dt/2, x[:,k] +k2/2)
k4 = dt * f(t[k]+dt/2, x[:,k] +k3)
dx =(k1+2*k2+2*k3+k4)/6

x[:,k+1] = x[:,k] + dx

  return(x,t)


params = {"r":0.01, "betaC":0.0025, "sT":20.0, "A":400.0, "a0": 0.01, "betaV": 0.00045, "B": 350.0, "alphaS": 0.02, "h": 0.0025, "sC":10.0, "k": 0.00001, "alphaV": 1.5,"alphaE":0.02, "alphaI": 0.025, "p":0.00001, "alphaC":1.5, "a1":0.015, "N":1000.0 }
f = lambda t,x : HIVmodel (x,params)
x0 = np.array([1000, 0, 0, 10, 10])
t0 = 0
tf = 2000
dt = 0.1

x,t = RungeKuttaOrder4(f, x0, t0, tf, dt)

寻找一些帮助来调试代码。 如果有人有另一种做 Runge Kutta 的方法，这是我正在使用的集成方法，那将非常有帮助。 我不确定我要去哪里错了。