类型错误：ufunc 的循环不支持没有可调用 sin 方法的 Add 类型的参数 0

Question

import math
import numpy as np
import matplotlib.pyplot as plt
import simpy as sp
init_printing()

var('x,y,z')

a = math.sqrt(10/7)    
c = (y-math.sqrt(18/7)-1)    
b = np.sin(math.pi/2*c)-z

f = lambda x,y,z: x**2+y**2+z**2-4
g = lambda x, y, z: (9/2)*(x**2+z**2)+y**2-9
h = lambda y, z: np.sqrt(10/7) * np.sin((np.pi/2) * y - np.sqrt(18/7)-1)- z
         
F = [[f(x, y, z)],
     [g(x, y, z)],
     [h(y, z)]]

As I try to define the fuction h(x) I get this:

AttributeError                            Traceback (most recent call last)
AttributeError: 'Add' object has no attribute 'sin'

The above exception was the direct cause of the following exception:

TypeError                                 Traceback (most recent call last)
<ipython-input-68-da3a7e28861c> in <module>

         10 a = math.sqrt(10/7)
     11 c = (y-math.sqrt(18/7)-1)
---> 12 b = np.sin((math.pi/2*c))-z
     13 
     14 

TypeError: loop of ufunc does not support argument 0 of type Add which has no callable sin method

I tried to separete the function in parts a, b and c so the error could be more easy to find. Now I know I have some problem with the var('x, y, z') and the np.sin()/math.sin() , but I can't find how to fix it.

Answer 1

Pay close attention to the type of the variables. When in doubt, check, don't just guess or assume

var('x,y,z')

these are sympy symbols (though here I'm guessing what var is doing)

a = math.sqrt(10/7)

this must be a python float, produced by the math.sqrt function.

c = (y-math.sqrt(18/7)-1)

Assuming y is sympy, then c itself is a sympy expression, probably an Add .

b = np.sin(math.pi/2*c)-z

math.pi/2*c is sympy expression.

np.sin is a numpy ufunc , and only works with numpy arrays. That means it first does

np.array(math.pi/2*c)

making a single element object dtype array.

np.sin given an object dtype array, passes the task to the sin method of that object. But noone defines a sin method. It's always a function.

Using np.sin , or many other numpy functions on sympy expressions just does not work. Don't mix sympy and numpy until you know what you are doing!

---

In [5]: sp.var('x,y,z')
Out[5]: (x, y, z)
In [6]: y
Out[6]: y
In [7]: a = math.sqrt(10/7)
   ...: c = (y-math.sqrt(18/7)-1)
In [8]: a
Out[8]: 1.1952286093343936
In [9]: c
Out[9]: y - 2.60356745147455
In [10]: type(c)
Out[10]: sympy.core.add.Add
In [11]: math.pi/2*c
Out[11]: 1.5707963267949*y - 4.08967418933897
In [12]: np.array(_)
Out[12]: array(1.5707963267949*y - 4.08967418933897, dtype=object)
In [13]: np.sin(_)
AttributeError: 'Add' object has no attribute 'sin'

The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "<ipython-input-13-2b409a55b2a2>", line 1, in <module>
    np.sin(_)
TypeError: loop of ufunc does not support argument 0 of type Add which has no callable sin method

pure sympy

In [14]: a = sp.sqrt(10/7)
    ...: c = (y-sp.sqrt(18/7)-1)
In [15]: c
Out[15]: y - 2.60356745147455
In [16]: sp.pi/2*c
Out[16]: pi*(y - 2.60356745147455)/2
In [17]: sp.sin(sp.pi/2*c)
Out[17]: sin(pi*(y/2 - 1.30178372573727))