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Slide the Kernel

The code behind the picture

Follow the lesson’s implementation, one code cell at a time.

Choose a language and read the cells in order. These are small teaching examples; the visual lesson runs separately.

Follow the calculation

Same inputs · Same operation · Same result

3 teaching cells · Python standard library · Read-only

1. Prepare the patch and the kernel
The 3 × 3 patch of the watermelon picture at the melon's right outline (brightness 0–9), and the kernel whose nine weights will be placed over it.
In [ ]:
```
import json

patch = [[0, 8, 8], [0, 8, 8], [5, 0, 8]]
kernel = [[-1, 0, 1], [-1, 0, 1], [-1, 0, 1]]
```
2. Multiply matching cells and add
Each weight multiplies the pixel directly under it, and the nine products are added into one response.
In [ ]:
```
result = sum(
    patch[i][j] * kernel[i][j]
    for i in range(3)
    for j in range(3)
)
```
3. Inspect the result
Print the result as JSON so both languages use the same output format.
In [ ]:
```
print(json.dumps(result))
```

Expected result

Running the three cells in order produces this result in either language.