How to remove the adjacent duplicate value in a numpy array?

Question

Given a numpy array, I wish to remove the adjacent duplicate non-zero value and all the zero value. For instance, for an array like that: [0,0,1,1,1,2,2,0,1,3,3,3]

Answer 1

>>> import numpy as NP
>>> a = NP.array([0,0,1,1,1,2,2,0,1,3,3,3])

first, remove the zeros:

>>> idx = a==0
>>> a = a[-idx1]
>>> a
  array([1, 1, 1, 2, 2, 1, 3, 3, 3])

now remove the consecutive duplicates

note that ediff1d(a) & a have different shapes, hence a1 is not the result; the leading value of a has to be pre-pended to it, as i did in the last three lines below)

>>> idx = NP.array(NP.ediff1d(a), dtype=bool)
>>> a1 = a[1:][idx]
  array([2, 1, 3])

create an empty array to store the result

>>> a0 = NP.empty(shape=(a1.shape[0]+1,))
>>> a0[0] = a[0]
>>> a0[1:] = a1
>>> a0
  array([ 1, 2, 1, 3])