title: TypeError: descriptor 'append' requires a 'list' object but received a 'numpy.float64'
body: <p>I don't understand how to fix the error in this case. I've already tried with numpy array, but the problem still presents.</p>
  
  <p>What I'm trying to do is: to calculate the runge function with the x for n iterations. For making this, I think that I have do put every single x in a list, and I do this with the <code>fill_cheby</code> function. After this, I want to use the numbers in <code>list1</code> as arguments of lagrange function in <code>runge_interpolate</code>. The problem is that I don't know how to append the elements in <code>list1</code>. Here the code and the complete traceback:</p>
  
  <pre><code>def fill_cheby(list1,n,x):
      if n==0:
          return n, x
      else:
          for i in range(0,n):
              x=np.cos(((2*(n-i)+1)*3.14)/(2*(n+1)))
              list1.append(x)
  
          return list1
  
  def runge_interpolate(n):
      p=lagrange(list1, runge(x))
      print("Il polinomio è ", p)
      return x, p
  
  list1=[]
  
  n=5
  x=0
  fill_cheby(list1,n,x)
  </code></pre>
  
  <p>Traceback (most recent call last):</p>
  
  <pre><code>File "arraycheby.py", line 33, in &lt;module&gt;
    fill_cheby(list,n,x)
  File "arraycheby.py", line 19, in fill_cheby
    list1.append(x)
  TypeError: descriptor 'append' requires a 'list' object but received a 'numpy.float64'
  </code></pre>