Issue #18219: Optimize csv.DictWriter for large number of columns.

Patch by Mariatta Wijaya.
This commit is contained in:
INADA Naoki 2016-10-21 19:47:57 +09:00
parent 4510e6de9d
commit 0a421a28f8
4 changed files with 28 additions and 5 deletions

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@ -195,10 +195,12 @@ The :mod:`csv` module defines the following classes:
written if the dictionary is missing a key in *fieldnames*. If the
dictionary passed to the :meth:`writerow` method contains a key not found in
*fieldnames*, the optional *extrasaction* parameter indicates what action to
take. If it is set to ``'raise'`` a :exc:`ValueError` is raised. If it is
set to ``'ignore'``, extra values in the dictionary are ignored. Any other
optional or keyword arguments are passed to the underlying :class:`writer`
instance.
take.
If it is set to ``'raise'``, the default value, a :exc:`ValueError`
is raised.
If it is set to ``'ignore'``, extra values in the dictionary are ignored.
Any other optional or keyword arguments are passed to the underlying
:class:`writer` instance.
Note that unlike the :class:`DictReader` class, the *fieldnames* parameter
of the :class:`DictWriter` is not optional. Since Python's :class:`dict`

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@ -145,7 +145,7 @@ class DictWriter:
def _dict_to_list(self, rowdict):
if self.extrasaction == "raise":
wrong_fields = [k for k in rowdict if k not in self.fieldnames]
wrong_fields = rowdict.keys() - self.fieldnames
if wrong_fields:
raise ValueError("dict contains fields not in fieldnames: "
+ ", ".join([repr(x) for x in wrong_fields]))

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@ -626,6 +626,24 @@ class TestDictFields(unittest.TestCase):
self.assertNotIn("'f2'", exception)
self.assertIn("1", exception)
def test_typo_in_extrasaction_raises_error(self):
fileobj = StringIO()
self.assertRaises(ValueError, csv.DictWriter, fileobj, ['f1', 'f2'],
extrasaction="raised")
def test_write_field_not_in_field_names_raise(self):
fileobj = StringIO()
writer = csv.DictWriter(fileobj, ['f1', 'f2'], extrasaction="raise")
dictrow = {'f0': 0, 'f1': 1, 'f2': 2, 'f3': 3}
self.assertRaises(ValueError, csv.DictWriter.writerow, writer, dictrow)
def test_write_field_not_in_field_names_ignore(self):
fileobj = StringIO()
writer = csv.DictWriter(fileobj, ['f1', 'f2'], extrasaction="ignore")
dictrow = {'f0': 0, 'f1': 1, 'f2': 2, 'f3': 3}
csv.DictWriter.writerow(writer, dictrow)
self.assertEqual(fileobj.getvalue(), "1,2\r\n")
def test_read_dict_fields(self):
with TemporaryFile("w+") as fileobj:
fileobj.write("1,2,abc\r\n")

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@ -20,6 +20,9 @@ Core and Builtins
Library
-------
- Issue #18219: Optimize csv.DictWriter for large number of columns.
Patch by Mariatta Wijaya.
- Issue #28448: Fix C implemented asyncio.Future didn't work on Windows.
- Issue #28480: Fix error building socket module when multithreading is