I don't know the meaning of the code "[:, row:row]"

Question

I have the code:

g, g_err = data[:, 4:6].T

I don't know the meaning of [:, 4:6]

especially the first :

and does .T mean transpose?

And here is an explanation for .T https://stackoverflow.com/questions/5741372/syntax-in-python-t — Vitali Avagyan, Sep 28 '19 at 11:44

score 1 · Answer 1 · edited Sep 28 '19 at 12:12

You have a 2D matrix called data, your code takes all elements from the first dimension, marked as :, then takes only elements 4 and 5 in the second dimension, something like this:

>>> np.ones( (7,7 ))
array([[ 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.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.,  1.,  1.]])
>>> np.ones( (7,7 ))[:,4:6]
array([[ 1.,  1.],
       [ 1.,  1.],
       [ 1.,  1.],
       [ 1.,  1.],
       [ 1.,  1.],
       [ 1.,  1.],
       [ 1.,  1.]])
>>>

And yeah, .T means transpose.

I don't know the meaning of the code "[:, row:row]"

1 Answers1