can't multiply sequence by non-int of type 'Add'

问题遇到的现象和发生背景

can't multiply sequence by non-int of type 'Add'

用代码块功能插入代码，请勿粘贴截图
import sympy
from scipy import integrate
from sympy import symbols

Vi = 350.0
Vj = 310.0
lamb_xy = 0.035
lamb_z = 0.015
Vij = 87.7
z = 1.0
sigma = 0.0147
sigmaz = sympy.sqrt(2) * sigma
sigmay = sympy.sqrt(2) * sigma
sigmax = sympy.sqrt(2) * sigma
P1 = 0.05
P2 = 0.95
t_min = float(1 / 36)
t_max = float(1 / 20)
t_av = float(1 / 24)
Hlong = 15.0
Casex = 1 / (sympy.sqrt(2 * sympy.pi) * sigmax)
Casey = 1 / (sympy.sqrt(2 * sympy.pi) * sigmay)
Casez = 1 / (sympy.sqrt(2 * sympy.pi) * sigmaz)
Case = (1 + (sympy.pi * lamb_xy * z) / (4 * lamb_z * Vij))
lamb_f = 1 / (t_av - t_min)
Ti = Hlong / Vj
# 碰撞概率
if Ti < t_min:
    CP_av = 0
    CR = 0
else:
    r = symbols('r')
    Ti = Ti + t_av
    P_y = lambda r: Casey * sympy.exp (-r ** 2 / (2 * sigmay ** 2))
    P_y = integrate.quad(P_y, -lamb_xy, lamb_xy)
    P_z = lambda r: Casez * sympy.exp (-r ** 2 / (2 * sigmaz ** 2))
    P_z = integrate.quad(P_z, -lamb_z, lamb_z)
    t = symbols('t')
    # S_x = Vi * (t + t_av) - Vj * t
    P_x = Casex * sympy.exp (-(r - (Vi * (t + t_av) - Vj * t)) ** 2 / (2 * sigmax ** 2))

    P_x = sympy.integrate(P_x,(r, [-lamb_xy, lamb_xy]))

    P = (P_x) * (P_y) * (P_z) * (Case)
    print(P)
    t_d = symbols('t_d')
    F = lamb_f * sympy.exp (-lamb_f * (t_d - t_min))

    CP = 1 / (Ti - t_d) * sympy.integrate(P,(t, 0, (Hlong - 1 / 36 * Vi) / 500))
    CP = P1 * P2 * CP * F
    CP_av =abs(sympy.integrate(CP,(t_d, [t_min, t_max])))
    CR = 2 * CP_av / (P1 * (Hlong - 1 / 36 * Vi) / Vi + P2 * Ti)
运行结果及报错内容

Traceback (most recent call last):
File "D:\crash project\数学.py", line 44, in
P = (P_x) * (P_y) * (P_z) * (Case)
TypeError: can't multiply sequence by non-int of type 'Add'

P_x P_y P_z Case四个变量的类型不一样，并且都不是可以作为相乘的类型，先转成可以相乘的类型再计算

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