The line of code `print(index[0][0])` is accessing the first element of the first dimension of the `index` variable.

The `index` variable is a NumPy array, and NumPy arrays can be multi-dimensional. In this case, the `index` variable is a 1-dimensional array, but it could be a 2-dimensional array, or even a higher-dimensional array.

The `[0][0]` notation is used to access elements in a multi-dimensional array. The first `[0]` refers to the first element of the first dimension, and the second `[0]` refers to the first element of the second dimension.

In this case, the `index` variable is a 1-dimensional array, so there is only one dimension. Therefore, the `[0][0]` notation is equivalent to just `[0]`.

So, the line of code `print(index[0][0])` is printing the value of the first element of the `index` variable. In this case, the value of the first element is 2, which is the index of the value 30 in the NumPy array.

I hope this explanation is helpful. Let me know if you have any other questions.

Here is a breakdown of the code:

```python
# Create a NumPy array
arr = np.array([10, 20, 30, 40, 50])

# Find the index of the value 30
index = np.where(arr == 30)

# Print the index
print(index)  # Output: (array([2]),)

# Print the first element of the index
print(index[0][0])  # Output: 2
```

The first line creates a NumPy array called `arr` with the values 10, 20, 30, 40, and 50.

The second line uses the `np.where()` function to find the index of the value 30 in the `arr` array. The `np.where()` function returns a tuple, where the first element is the indices of the elements that satisfy the condition, and the second element is the corresponding values. In this case, the first element of the tuple is a 1-dimensional array with the single element 2, which is the index of the value 30 in the `arr` array.

The third line prints the value of the `index` variable. The output is a tuple, where the first element is a 1-dimensional array with the single element 2, which is the index of the value 30 in the `arr` array.

The fourth line prints the first element of the `index` variable. The output is 2, which is the index of the value 30 in the `arr` array.
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