[DEREK] You cannot create a regular 2-dimensional integer array from one row of length 3

and a second one of length 0. Thus np.array chooses the next most basic type of
array it can fit your input data in

Which is the case, only if an second one of length 0 is given.

What about the case 1 :

>>> x12 = np.array([[1,2,3]])

>>> x12

array([[1, 2, 3]])

>>> print(x12)

[[1 2 3]]

>>> x12.ndim

2

>>>

This seems to take 2 dimension.

I presumed the above case and the case where length 0 is provided to be treated same(I mean same behaviour).

Correct me if I am wrong.

Also, could u please point out any documentation to understand the logic behind creating elements of type list in case 2(with second grid of length 0) ? If possible. I am curious to understand.

Kind Rgds,

Vinodhini B

On 30 Dec 2017, at 11:36 PM, Derek Homeier <derek@astro.physik.uni-goettingen.de> wrote:

On 30 Dec 2017, at 11:37 am, Vinodhini Balusamy <me.vinob@gmail.com> wrote:

Case 2:

x12 = np.array([[1,2,3],[]])
x12.ndim
1
print(x12)
[list([1, 2, 3]) list([])]

In case 2, I am trying to understand why it becomes 1 dimentional ?!?!

Case 3:

x12 = np.array([1,2,3])
x12.ndim
1
print(x12)
[1 2 3]

This seems reasonable to me to be considered as 1 dimensional.

Would like to understand case 2 a bit more to get to know if i am missing something.
Will be much appreciated if someone to explain me a bit.

Welcome to the crowd!
You cannot create a regular 2-dimensional integer array from one row of length 3
and a second one of length 0. Thus np.array chooses the next most basic type of
array it can fit your input data in - you will notice in case 2 the array actually has two
elements of type ‘list’, and you can verify that

In [1]: x12 = np.array([[1,2,3],[]])
In [2]: x12.dtype
Out[2]: dtype('O')
In [3]: x12.shape
Out[3]: (2,)

i.e. it has created an array of dtype ‘object’, which is probably not what you expected
(and nothing you could perform standard arithmetic operations on:

In [4]: x12+1
TypeError: can only concatenate list (not "int") to list

HTH
Derek

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