title: append() takes at least 2 arguments (1 given)?
body: <p>I am trying to solve a for the real roots of my cubic equation where my coefficnets are actually arrays. I was able to find the roots but I am also trying to append all the real roots into a separtae array so I can use it for my other problems. I am not sure what I am doing wrong. The error that comes out is:</p>
  
  <blockquote>
    <p>append() takes at least 2 arguments (1 given).</p>
  </blockquote>
  
  <p>P.S: <code>gradU_all</code> is some array that I have previously defined.</p>
  
  <p>MY CODE STARTS HERE: (ignore the weird format)</p>
  
  <pre><code>S=gradU_all
  
  print S.shape
  
  Wi=50
  
  L=10
  
  a=2*S**2*Wi**2
  
  print a.shape
  
  b=0
  
  c=np.ones(N+2)
  
  c*=L**2
  
  c+=3
  
  print c.shape
  
  d=np.ones(N+2)
  
  d*=-L**2
  
  print d.shape
  
  
  def Find_psi_real_roots():
  
      psi_real_roots=np.zeros(N+2)
      for i in range(N+2):
          #print 'for i:', i
          coeff= [a[i],0,103,-100]
          r=np.roots(coeff)
          real_valued = r.real[abs(r.imag)==0]
          psi_real_roots=np.append(real_valued[i])
  
  
  Find_psi_real_roots()
  </code></pre>