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Python Sympy将符号矩阵替换为（转换为）符号

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q_vec, omega_vec, q1, q2, q3, w1, w2, w3 = \
        sym.symbols('q_vec, omega_vec, q1, q2, q3, w1, w2, w3')

q_0_dot_str = '.5 * dot(q_vec, omega_vec)'
q_0_dot_symp = sym.sympify(q_0_dot_str)
q_0_dot_symp = q_0_dot_symp.subs([(q_vec, sym.Matrix([q1, q2, q3]), \
                               (omega_vec, sym.Matrix([w1, w2, w3]).T))])
q_0_dot_fcn = lambdify((q1, q2, q3, w1, w2, w3), q_0_dot_symp, 'numpy')

-要么-

q_0_dot_str = '.5 * dot(q_vec, omega_vec)'
q_0_dot_symp = sym.sympify(q_0_dot_str)
q_0_dot_symp = q_0_dot_symp.subs([(q_vec, sym.Matrix([q1, q2, q3]), \
                               (omega_vec, sym.Matrix([w1, w2, w3]).T))])
q_0_dot_symp = q_0_dot_symp.xreplace([{q_vec: sym.Matrix([q1, q2, q3])},\
                                   {omega_vec: sym.Matrix([w1, w2, w3]).T}])
q_0_dot_fcn = lambdify((q1, q2, q3, w1, w2, w3), q_0_dot_symp, 'numpy')

但这些都不奏效 . 当我评估以下内容时：

q_0_dot_fcn(1,2,3,4,5,6)

我明白了：

0.5*omega_vec*q_vec

而不是它为我在符号矩阵中提供的符号变量提供的值（然后获得实际的m =数值结果） .

python matrix sympy lambdify

1 回答

  • 0

    您在子调用中输入了一个拼写错误 . 它应该是

    q_0_dot_symp = q_0_dot_symp.subs([(q_vec, sym.Matrix([q1, q2, q3])), \
                               (omega_vec, sym.Matrix([w1, w2, w3]).T)])

    代替

    q_0_dot_symp = q_0_dot_symp.subs([(q_vec, sym.Matrix([q1, q2, q3]), \
                               (omega_vec, sym.Matrix([w1, w2, w3]).T))])

    （注意括号的位置）

    完成此修复后，它在SymPy 1.0中适用于我

    In [1]: import sympy as sym

In [2]: q_vec, omega_vec, q1, q2, q3, w1, w2, w3 = \
   ...:         sym.symbols('q_vec, omega_vec, q1, q2, q3, w1, w2, w3')

In [3]: q_0_dot_str = '.5 * dot(q_vec, omega_vec)'

In [4]: q_0_dot_symp = sym.sympify(q_0_dot_str)

In [5]: q_0_dot_symp = q_0_dot_symp.subs([(q_vec, sym.Matrix([q1, q2, q3])), \
                               (omega_vec, sym.Matrix([w1, w2, w3]).T)])

In [6]: q_0_dot_fcn = lambdify((q1, q2, q3, w1, w2, w3), q_0_dot_symp, 'numpy')

In [7]: q_0_dot_fcn(1,2,3,4,5,6)
Out[7]:
array([[ 2. ,  2.5,  3. ],
       [ 4. ,  5. ,  6. ],
       [ 6. ,  7.5,  9. ]])
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