Row expansion question

[akramer24]

Hello,

I am experimenting with perspective-python as a backend solution for a pivot table. I'm having some trouble understanding how row expansion works. When I pivot a view and attempt to expand a row, get_row_expanded subsequently tells me the row is not expanded and I also do not see the expanded row's children in view.to_records(). A simple repro is below. Any guidance you could provide would be greatly appreciated.

my_table = perspective.Table(
    pd.DataFrame(
        [
            ["Fruit", "Apple", 10],
            ["Fruit", "Orange", 5],
            ["Fruit", "Strawberry", 12],
            ["Vegetable", "Potato", 8],
            ["Vegetable", "Carrot", 4],
        ],
        columns=["Category", "Item", "Quantity"],
    ),
    index="index",
)
pivoted = my_table.view(group_by=["Category"], columns=["Quantity"])
print(
    pivoted.to_records()
)  # [{'__ROW_PATH__': [], 'Quantity': 39}, {'__ROW_PATH__': ['Fruit'], 'Quantity': 27}, {'__ROW_PATH__': ['Vegetable'], 'Quantity': 12}]
print(pivoted.get_row_expanded(1))  # False
print(pivoted.get_row_expanded(2))  # False
pivoted.expand(1)
print(
    pivoted.to_records()
)  # [{'__ROW_PATH__': [], 'Quantity': 39}, {'__ROW_PATH__': ['Fruit'], 'Quantity': 27}, {'__ROW_PATH__': ['Vegetable'], 'Quantity': 12}]
print(pivoted.get_row_expanded(1))  # False

[texodus]

Your problem isn't with row expansion, rather this is not how group-by works. You can't expand the "Fruit" row because this is a leaf node, there are no children because you've only applied a single pivot level. Please check the documentation for group_by, or any of the interactive examples on the perspective docs site that feature group-by operations.

If you want a pivot table, use perspective-viewer - there is nothing in the perspective-python API which is not 1:1 already implemented in the perspective-viewer UI. If you want a master-detail view, here is an example.

[akramer24]

Thank you for the quick response. This was helpful. I didn't realize I was using group_by incorrectly.