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>>> a = np.empty(3,dtype = np.int)
>>> a[0] = 2
>>> a[1] = 1
>>> a[2] = 5
>>> a = np.append(a,3)
>>> a
array([2, 1, 5, 3])
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>>> a = np.array([],dtype = int)
>>> a = np.append(a,2)
>>> a = np.append(a,1)
>>> a = np.append(a,3)
>>> a = np.append(a,5)
>>> a
array([2, 1, 3, 5])