为什么我不能通过python生成器运行linspace（）？（初学者）

Question

我的函数使用一种方法来计算一个三次方程的系数，然后运行一个for循环并生成。然后，我在函数外部使用另一个for循环对其进行迭代，以调用它，并从三次方程中列出根

我可以在输入标量值时运行它，但当我将其中一个变量作为带有np.linspace()的序列放置时，它会输出The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

这是我的密码：

Tlnh = np.linspace(18,100,10)
Tch = 33.145 #K
Pch = 1.2964 #MPa
Dch = 31.263 #kg/m3
wh = -0.219 
 
def root((T,P,Tc,Pc,w, R=8.314):
      .
      .
      .

      #Using np.roots() and only printing out the real positive number
      coeff = [1,p1, p2, p3]
      roots = np.roots(coeff)

      #prints out the real positive roots only. 
      for i in range(len(roots)):
          if np.isreal(roots[i]):
          return np.real(roots[i]) 

      return 

g = [h for h in root(Tlnh,p1h,Tch,Pch,wh)]

输出：

ValueError                                Traceback (most recent call last)
<ipython-input-78-4b4a96b379ea> in <module>
      1 #Hydrogen Densities for Pr = 0.8
      2 #r =[h for h in root(Tlnh,p1h,Tch,Pch)]
----> 3 g = [h for h in root(Tlnh,p1h,Tch,Pch,wh)]
      4 print(g)

<ipython-input-76-20726dad64bd> in root(T, P, Tc, Pc, w, R)
     44     #Using np.roots() and only printing out the real positive number
     45     coeff = [1,p1, p2, p3]
---> 46     roots = np.roots(coeff)
     47 
     48     #prints out the real positive roots only.

<__array_function__ internals> in roots(*args, **kwargs)

D:\anaconda3\lib\site-packages\numpy\lib\polynomial.py in roots(p)
    220 
    221     # find non-zero array entries
--> 222     non_zero = NX.nonzero(NX.ravel(p))[0]
    223 
    224     # Return an empty array if polynomial is all zeros

<__array_function__ internals> in nonzero(*args, **kwargs)

D:\anaconda3\lib\site-packages\numpy\core\fromnumeric.py in nonzero(a)
   1906 
   1907     """
-> 1908     return _wrapfunc(a, 'nonzero')
   1909 
   1910 

D:\anaconda3\lib\site-packages\numpy\core\fromnumeric.py in _wrapfunc(obj, method, *args, **kwds)
     56 
     57     try:
---> 58         return bound(*args, **kwds)
     59     except TypeError:
     60         # A TypeError occurs if the object does have such a method in its

    ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all(

)

Answer 1

EDIT:np.roots是一个有问题的调用，因为它需要一个1d的系数数组。每个系数必须是一个数字，而不是一个数组

原始答复供参考：

The problem is most probably in the line:

if np.isreal(...):

(in theory, you should have gotten a traceback pinpointing the line).

But why? Well, the function gives you something like:

if [True, False, False, True, ....]:

Now how should the if operator interpret this result? Is it True or False? Answer: It gives up and throws you the error you observed.