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add __len__ and __getitem__ to Column #140

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Merged
merged 11 commits into from
May 4, 2023
Merged

add __len__ and __getitem__ to Column #140

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e689f0b
add __len__ and __getitem__ to Column
Apr 17, 2023
1fa1030
remove trailing whitespace
Apr 17, 2023
faaf599
Revert "remove trailing whitespace"
Apr 17, 2023
8b2413b
type getitems row
Apr 18, 2023
27a1ece
let __getitem__ take sequence of int
Apr 19, 2023
73e7987
Revert "let __getitem__ take sequence of int"
Apr 19, 2023
ce443f8
add get_rows
Apr 19, 2023
2796b0d
Merge remote-tracking branch 'upstream/main' into column-getitem-and-len
Apr 19, 2023
41eb73d
Merge remote-tracking branch 'upstream/main' into column-getitem-and-len
Apr 27, 2023
d5440e8
Merge remote-tracking branch 'upstream/main' into column-getitem-and-len
Apr 28, 2023
995ec3a
doc fixup
Apr 28, 2023
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24 changes: 23 additions & 1 deletion spec/API_specification/dataframe_api/column_object.py
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Original file line number Diff line number Diff line change
@@ -1,2 +1,24 @@
from typing import NoReturn

class Column:
pass
def __len__(self) -> int:
"""
Return the number of rows.
"""

def __getitem__(self, row) -> object:
"""
Get the element at row index `row`.
"""
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What is the expected type of "row" here? An integer?

I wonder if we should have more explicit methods than __getitem__ since intuitively people will try to feed both scalars and Sequences / Columns into it.

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oops, forgot to annotate that one, thanks

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I wonder if we should have more explicit methods than getitem since intuitively people will try to feed both scalars and Sequences / Columns into it.

could you expand please?

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Historically, Pandas and other dataframe libraries have allowed passing scalar-like objects here and getting a scalar-like object in return or passing Sequence-like / Column-like objects here and getting Column-like objects in return. I.E. for Pandas:

import pandas as pd

pds = pd.Series(['a', 'b', 'c', 'd', 'e'])

print(pds[0])  # Scalar-like input --> Scalar-like output
print(pds[[0]])  # Sequence-like input --> Column-like output

For our DataFrame object we have the get_rows method that takes a Sequence-like (should probably take a Column-like) where we could presumably have the same function for our Column object, and then instead of using __getitem__ we could have something like get_element or get_scalar or something like that.

If we wanted to keep the __getitem__ method I would suggest we handle both the Scalar-like and Sequence-like / Column-like cases as opposed to just the Scalar-like.

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we have the get_rows method that takes a Sequence-like (should probably take a Column-like)

yeah, I came across this - I'll open a separate issue

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@MarcoGorelli MarcoGorelli Apr 19, 2023 •
edited
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If we wanted to keep the getitem method I would suggest we handle both the Scalar-like and Sequence-like / Column-like cases as opposed to just the Scalar-like.

I've pushed a commit but am not overly keen on it, how about Column.get_rows?

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added another commit with get_rows, better to avoid overloads if we can help it


def __iter__(self) -> NoReturn:
"""
Iterate over elements.

This is intentionally "poisoned" to discourage inefficient code patterns.

Raises
------
NotImplementedError
"""
raise NotImplementedError("'__iter__' is intentionally not implemented.")