p=array_2
q=array_2
p=numpy.vstack([p,q])

a = np.ones((20,100,3))
b = np.vstack((a,a))

print b.shape # (40,100,3)

b = np.concatenate((a,a),axis=0)

In [172]: a = np.random.normal(size=(20,100,3))

In [173]: c = np.random.normal(size=(20,100,3))

In [174]: %timeit b = np.concatenate((a,c),axis=0)
100000 loops, best of 3: 13.3 us per loop

In [175]: %timeit b = np.vstack((a,c))
10000 loops, best of 3: 26.1 us per loop

np.concatenate((a1, a2, ...), axis=0)

>>> from scipy import *
>>> a = rand(20,100,3)
>>> b = rand(20,100,3)
>>> a.shape
(20, 100, 3)
>>> b.shape
(20, 100, 3)
>>> r_[a,b].shape
(40, 100, 3)
>>> (r_[a,b] == vstack([a,b])).all()
True