Issue #13573: The csv.writer now uses the repr() for floats rather than str().

1 files changed, 14 insertions, 2 deletions

diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 7b16e2db64..681cfd8e85 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -207,6 +207,18 @@ class Test_Csv(unittest.TestCase):
             fileobj.close()
             os.unlink(name)
 
+    def test_write_float(self):
+        # Issue 13573: loss of precision because csv.writer
+        # uses str() for floats instead of repr()
+        orig_row = [1.234567890123, 1.0/7.0, 'abc']
+        f = StringIO()
+        c = csv.writer(f, quoting=csv.QUOTE_NONNUMERIC)
+        c.writerow(orig_row)
+        f.seek(0)
+        c = csv.reader(f, quoting=csv.QUOTE_NONNUMERIC)
+        new_row = next(c)
+        self.assertEqual(orig_row, new_row)
+
     def _read_test(self, input, expect, **kwargs):
         reader = csv.reader(input, **kwargs)
         result = list(reader)
@@ -784,7 +796,7 @@ class TestArrayWrites(unittest.TestCase):
         try:
             writer = csv.writer(fileobj, dialect="excel")
             writer.writerow(a)
-            expected = ",".join([str(i) for i in a])+"\r\n"
+            expected = ",".join([repr(i) for i in a])+"\r\n"
             fileobj.seek(0)
             self.assertEqual(fileobj.read(), expected)
         finally:
@@ -800,7 +812,7 @@ class TestArrayWrites(unittest.TestCase):
         try:
             writer = csv.writer(fileobj, dialect="excel")
             writer.writerow(a)
-            expected = ",".join([str(i) for i in a])+"\r\n"
+            expected = ",".join([repr(i) for i in a])+"\r\n"
             fileobj.seek(0)
             self.assertEqual(fileobj.read(), expected)
         finally: