cool and efficient code in numpy.

numpy_code_tricks

 1. sort an array by the nth column
  Z = np.random.randint(0,10,(3,3))
  print(Z)
  print(Z[Z[:,1].argsort()])
  
 2. Find the nearest value from a given value in an array
    m = Z.flat[np.abs(Z - z).argmin()]
    
 3. accumulate elements of a vector (X) to an array (F) based on an index list (I)
    X = [1,2,3,4,5,6]
    I = [1,3,9,3,4,1]
    F = np.bincount(I,X)