bpo-32255: Always quote a single empty field when write into a CSV file. (#4769)
This allows to distinguish an empty row from a row consisting of a single empty field.
diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 03ab184..fe24801 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -207,10 +207,29 @@
with TemporaryFile("w+", newline='') as fileobj:
writer = csv.writer(fileobj)
self.assertRaises(TypeError, writer.writerows, None)
- writer.writerows([['a','b'],['c','d']])
+ writer.writerows([['a', 'b'], ['c', 'd']])
fileobj.seek(0)
self.assertEqual(fileobj.read(), "a,b\r\nc,d\r\n")
+ def test_writerows_with_none(self):
+ with TemporaryFile("w+", newline='') as fileobj:
+ writer = csv.writer(fileobj)
+ writer.writerows([['a', None], [None, 'd']])
+ fileobj.seek(0)
+ self.assertEqual(fileobj.read(), "a,\r\n,d\r\n")
+
+ with TemporaryFile("w+", newline='') as fileobj:
+ writer = csv.writer(fileobj)
+ writer.writerows([[None], ['a']])
+ fileobj.seek(0)
+ self.assertEqual(fileobj.read(), '""\r\na\r\n')
+
+ with TemporaryFile("w+", newline='') as fileobj:
+ writer = csv.writer(fileobj)
+ writer.writerows([['a'], [None]])
+ fileobj.seek(0)
+ self.assertEqual(fileobj.read(), 'a\r\n""\r\n')
+
@support.cpython_only
def test_writerows_legacy_strings(self):
import _testcapi
diff --git a/Misc/ACKS b/Misc/ACKS
index 54d8d62..8303ce8 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1554,6 +1554,7 @@
Arfrever Frehtes Taifersar Arahesis
Hideaki Takahashi
Takase Arihiro
+Licht Takeuchi
Indra Talip
Neil Tallim
Geoff Talvola
diff --git a/Misc/NEWS.d/next/Library/2017-12-12-07-29-06.bpo-32255.2bfNmM.rst b/Misc/NEWS.d/next/Library/2017-12-12-07-29-06.bpo-32255.2bfNmM.rst
new file mode 100644
index 0000000..dafee67
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-12-12-07-29-06.bpo-32255.2bfNmM.rst
@@ -0,0 +1,3 @@
+A single empty field is now always quoted when written into a CSV file.
+This allows to distinguish an empty row from a row consisting of a single empty field.
+Patch by Licht Takeuchi.
diff --git a/Modules/_csv.c b/Modules/_csv.c
index 5314ef6..e616151 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -1238,7 +1238,7 @@
if (PyErr_Occurred())
return NULL;
- if (self->num_fields > 0 && self->rec_size == 0) {
+ if (self->num_fields > 0 && self->rec_len == 0) {
if (dialect->quoting == QUOTE_NONE) {
PyErr_Format(_csvstate_global->error_obj,
"single empty field record must be quoted");