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https://issues.apache.org/jira/browse/ARROW-2453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16446972#comment-16446972
]
ASF GitHub Bot commented on ARROW-2453:
---------------------------------------
xhochy closed pull request #1923: ARROW-2453: [Python] Improve Table column
access
URL: https://github.com/apache/arrow/pull/1923
This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:
As this is a foreign pull request (from a fork), the diff is supplied
below (as it won't show otherwise due to GitHub magic):
diff --git a/python/pyarrow/table.pxi b/python/pyarrow/table.pxi
index cbf2a69f7..cbbfe7da8 100644
--- a/python/pyarrow/table.pxi
+++ b/python/pyarrow/table.pxi
@@ -1152,7 +1152,30 @@ cdef class Table:
self._check_nullptr()
return pyarrow_wrap_schema(self.table.schema())
- def column(self, int i):
+ def column(self, i):
+ """
+ Select a column by its column name, or numeric index.
+
+ Parameters
+ ----------
+ i : int or string
+
+ Returns
+ -------
+ pyarrow.Column
+ """
+ if isinstance(i, six.string_types):
+ field_index = self.schema.get_field_index(i)
+ if field_index < 0:
+ raise KeyError("Column {} does not exist in table".format(i))
+ else:
+ return self._column(field_index)
+ elif isinstance(i, six.integer_types):
+ return self._column(i)
+ else:
+ raise TypeError("Index must either be string or integer")
+
+ def _column(self, int i):
"""
Select a column by its numeric index.
diff --git a/python/pyarrow/tests/test_table.py
b/python/pyarrow/tests/test_table.py
index 5303cb219..492cf0089 100644
--- a/python/pyarrow/tests/test_table.py
+++ b/python/pyarrow/tests/test_table.py
@@ -301,6 +301,23 @@ def test_table_from_arrays_invalid_names():
pa.Table.from_arrays(data, names=['a'])
+def test_table_select_column():
+ data = [
+ pa.array(range(5)),
+ pa.array([-10, -5, 0, 5, 10]),
+ pa.array(range(5, 10))
+ ]
+ table = pa.Table.from_arrays(data, names=('a', 'b', 'c'))
+
+ assert table.column('a').equals(table.column(0))
+
+ with pytest.raises(KeyError):
+ table.column('d')
+
+ with pytest.raises(TypeError):
+ table.column(None)
+
+
def test_table_add_column():
data = [
pa.array(range(5)),
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> [Python] Improve Table column access
> ------------------------------------
>
> Key: ARROW-2453
> URL: https://issues.apache.org/jira/browse/ARROW-2453
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Python
> Affects Versions: 0.9.0
> Reporter: Antoine Pitrou
> Assignee: Kee Chong Tan
> Priority: Major
> Labels: beginner, pull-request-available
> Fix For: 0.10.0
>
>
> Suppose you have a table column named "nulls". Right now, to access it on a
> table, you need to do something like this:
> {code:python}
> >>> table.column(table.schema.get_field_index('nulls'))
> <pyarrow.lib.Column object at 0x7fe4144d2570>
> chunk 0: <pyarrow.lib.NullArray object at 0x7fe3db51b4a8>
> [
> NA,
> NA,
> NA
> ]
> {code}
> Also, if you mistype the column name, instead of getting an error you get an
> arbitrary column:
> {code}
> >>> table.column(table.schema.get_field_index('z'))
> <pyarrow.lib.Column object at 0x7fe3dbd6cc30>
> chunk 0: <pyarrow.lib.Int64Array object at 0x7fe3db54b408>
> [
> 0,
> 1,
> 2
> ]
> {code}
> {{Table.column()}} should accept a string object and return the column with
> the corresponding name. KeyError should be raised if there is no column with
> a such name.
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