[Tutor] difference between array([1,0,1]) and array([[1,0,1]])

[Mats Wichmann]

On 6/20/19 5:39 PM, Markos wrote:
> Hi,
> 
> I'm studying Numpy and I don't understand the difference between
> 
>>>> vector_1 = np.array( [ 1,0,1 ] )
> 
> with 1 bracket and
> 
>>>> vector_2 = np.array( [ [ 1,0,1 ] ] )
> 
> with 2 brackets

the first is one-dimensional, the second two-dimensional.  If we expand
how we write the second a bit does it make it more clear?

np.array([
   [1, 0, 1],
   # no other elements
])

the double brackets look magical, but as soon as you have more than one
row it makes sense.

> 
> The shape of vector_1 is:
> 
>>>> vector_1.shape
> (3,)
> 
> But the shape of vector_2 is:
> 
>>>> vector_2.shape
> (1, 3)
> 
> The transpose on vector_1 don't work:
> 
>>>> vector_1.T
> array([1, 0, 1])
> 
> But the transpose method in vector_2 works fine:
> 
>>>> vector_2.T
> array([[1],
>        [0],
>        [1]])
> 
> 
> I thought that both vectors would be treated as an matrix of 1 row and 3
> columns.
> 
> Why this difference?
> 
> Any tip?
> 
> Thank you,
> Markos
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