[Python-checkins] cpython (merge 3.6 -> default): Issue #18219: Optimize csv.DictWriter for large number of columns.
inada.naoki
python-checkins at python.org
Fri Oct 21 08:18:06 EDT 2016
https://hg.python.org/cpython/rev/6f1602dfa4d5
changeset: 104604:6f1602dfa4d5
parent: 104602:307d7b47b06a
parent: 104603:1928074e6519
user: INADA Naoki <songofacandy at gmail.com>
date: Fri Oct 21 19:53:30 2016 +0900
summary:
Issue #18219: Optimize csv.DictWriter for large number of columns.
Patch by Mariatta Wijaya.
files:
Doc/library/csv.rst | 10 ++++++----
Lib/csv.py | 2 +-
Lib/test/test_csv.py | 18 ++++++++++++++++++
Misc/NEWS | 3 +++
4 files changed, 28 insertions(+), 5 deletions(-)
diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
--- a/Doc/library/csv.rst
+++ b/Doc/library/csv.rst
@@ -195,10 +195,12 @@
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`
diff --git a/Lib/csv.py b/Lib/csv.py
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -145,7 +145,7 @@
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]))
diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -626,6 +626,24 @@
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")
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -88,6 +88,9 @@
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 #23214: In the "io" module, the argument to BufferedReader and
--
Repository URL: https://hg.python.org/cpython
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