利用numpy构造pandas

a= abs(np.random.normal(0, 2, size=(70,1)))
b= abs(np.random.normal(10, 3, size=(70,1)))
c= abs(np.random.normal(20, 3, size=(70,1)))

data1 =np.vstack((a, b, c))
gn= ['a']*a.shape[0]+['b']*b.shape[0]+['c']*c.shape[0]

date2 = pd.DataFrame()
date2['V'] =np.squeeze(data1)
date2['G'] = gn