需要对一个方程组求导，然后循环赋值之后导出，现在就是在循环中赋值时出现了问题，希望有人能帮忙看一下。
B_scs = []
for i in range(5):
for j in range(len(nums)):
x_x0_s = float(x_x0.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3:b_3n[i],c_1:c_1n[i],c_2:c_2n[i],c_3:c_3n[i],X:X[j],Y:Y[j],Z:Z[j]}))
x_y0_s = float(x_y0.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_f_s = float(x_f.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_k1_s = float(x_k1.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_k2_s = float(x_k2.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_k3_s = float(x_k3.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_b1_s = float(x_b1.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_b2_s = float(x_b2.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_p1_s = float(x_p1.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))
x_p2_s = float(x_p2.evalf(subs={XS: XS[i], YS: YS[i], ZS: ZS[i], a_1: a_1n[i], a_2: a_2n[i], a_3: a_3n[i], b_1: b_1n[i], b_2: b_2n[i],b_3: b_3n[i], c_1: c_1n[i], c_2: c_2n[i], c_3: c_3n[i], X: X[j], Y: Y[j], Z: Z[j]}))