rlee827 - 1 year ago 178

Python Question

If I run the following:

`import numpy as np`

a = np.arange(9)

a = a.reshape((3,3))

I will get this:

`a = [[0 1 2]`

[3 4 5]

[6 7 8]]

If I create a larger array like this:

`b = np.zeros((5,5))`

b = [[ 0. 0. 0. 0. 0.]

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

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

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

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

How do I efficiently copy

`a`

`b`

`# border of 0 surrounding a to be filled in with other data later`

b = [[ 0. 0. 0. 0. 0.]

[ 0. 1. 2. 3. 0.]

[ 0. 4. 5. 6. 0.]

[ 0. 7. 8. 9. 0.]

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

I am looking for a function built into

`numpy`

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Answer Source

You can specify `b[1:4, 1:4]`

to denote the part:

```
>>> import numpy as np
>>> a = np.arange(9)
>>> a = a.reshape((3, 3))
>>> b = np.zeros((5, 5))
>>> b[1:4, 1:4] = a
>>> b
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 1., 2., 0.],
[ 0., 3., 4., 5., 0.],
[ 0., 6., 7., 8., 0.],
[ 0., 0., 0., 0., 0.]])
>>> b[1:4,1:4] = a + 1 # If you really meant `[1, 2, ..., 9]`
>>> b
array([[ 0., 0., 0., 0., 0.],
[ 0., 1., 2., 3., 0.],
[ 0., 4., 5., 6., 0.],
[ 0., 7., 8., 9., 0.],
[ 0., 0., 0., 0., 0.]])
```

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