蟒提取n列

Question

我有格式的numpy的數組：

a = [[1,2,3],[4,5,6],[7,8,9]] 

我要提取的元素爲：

a' = [[1,2],[4,5],[7,8]] 

我嘗試使用：

a' = a[:][:2] 

但它不像我預期的那樣工作

Answer 1

>>> numpy.array([[1,2,3],[4,5,6],[7,8,9]])[:,:2] 
array([[1, 2], 
     [4, 5], 
     [7, 8]]) 

Answer 2

>>> [l[:2] for l in a] 
[[1, 2], [4, 5], [7, 8]]