Numpy 1D array[x] と 2D array[x,1]の違い

Python初心者のメモ。内容の間違いなどご注意ください。

import numpy as np

def test():
    a = np.zeros([5,1]) #2D array columnができる
    b = np.ones([5]) #1D array　columnなし。
    
    print a 
    print 
    print "Dimension a: ", a.shape 
    print 
    print b, b.shape
    print 
    print "Dimension b: ", b.shape 
    print
    print a + b ＃1D + 2Dの演算になる
    print 
    
    a = np.squeeze(a)
    print a, #1D に変更
    print 
    print a + b
    
if __name__ == '__main__':
    test()

Output:

[[ 0.]
[ 0.]
[ 0.]
[ 0.]
[ 0.]]

Dimension a:  (5, 1)

[ 1.  1.  1.  1.  1.] (5,)

Dimension b:  (5,)

[[ 1.  1.  1.  1.  1.]
[ 1.  1.  1.  1.  1.]
[ 1.  1.  1.  1.  1.]
[ 1.  1.  1.  1.  1.]
[ 1.  1.  1.  1.  1.]]

[ 0.  0.  0.  0.  0.]
[ 1.  1.  1.  1.  1.]