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Implemented DataFrame.lookup #1785

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@itholic itholic commented Sep 22, 2020

This PR proposes DataFrame.lookup.

>>> kdf = ks.DataFrame({'A': [3, 4, 5, 6, 7],
...                     'B': [10.0, 20.0, 30.0, 40.0, 50.0],
...                     'C': ['a', 'b', 'c', 'd', 'e']})
>>> kdf
   A     B  C
0  3  10.0  a
1  4  20.0  b
2  5  30.0  c
3  6  40.0  d
4  7  50.0  e

>>> kdf.lookup([0], ["C"])
array(['a'], dtype=object)

>>> kdf.lookup([2, 3], ["A", "B"])
array([ 5., 40.])

databricks/koalas/frame.py Outdated Show resolved Hide resolved
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itholic commented Sep 24, 2020

Thanks, @HyukjinKwon

databricks/koalas/tests/test_dataframe.py Show resolved Hide resolved
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itholic commented Sep 26, 2020

Thanks, @ueshin

raise ValueError("Row labels must have same size as column labels")
lookups = [
self.loc[row_label, col_label]
for row_label, col_label in zip(row_labels, col_labels)
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Does this mean we launch jobs as many as labels?

@@ -10277,7 +10277,7 @@ def lookup(self, row_labels, col_labels) -> np.ndarray:
lookups = [
self.loc[row_label, col_label] for row_label, col_label in zip(row_labels, col_labels)
]
return Series(lookups).to_numpy()
return np.asarray(pd.Series(lookups))
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Out of curiosity, why did we change it to np.asarray(pd.Series(lookups))?

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4 participants