title: Can't assign to function call
body: <p>I am writing a code in python,Opencv for implementing a Gaussian low pass filter on compiling it gives the error 'can't assign to function call' at line 14 which is where I take square root .</p>
  
  <pre><code>`import cv2
  import numpy as np
  from math import sqrt
  img = cv2.imread('polys.jpg',0)
  f = np.fft.fft2(img)
  fshift = np.fft.fftshift(f)
  magnitude_spectrum = 20*np.log(np.abs(fshift))
  m, n = img.shape
  m2,n2 = m/2 , n/2
  d=np.zeros((m,n))
  for u in range(m):
  for v in range(n):
      r=((u-m2)*(u-m2))+((v-n2)*(v-n2))
      d(u,v)=sqrt(r)
      d(u,v)=int(d(u,v))
      if d(u,v)&gt;10:
         h(u,v)=0
      elif d(u,v)&lt;=10:
         h(u,v)= math.exp(-(d(u,v)*d(u,v))/(2*10*10))
  
  result=h*fshift    
  f_ishift = np.fft.ifftshift(result)
  img_back = np.fft.ifft2(f_ishift)
  img_back = np.abs(img_back)
  
  
  cv2.imshow('dft',img_back)
  cv2.waitKey(0)
  cv2.destroyAllWindows()
  </code></pre>
  
  <p>`</p>