From be0698b1ad096d8bd6564fa06486f2fcea47cac9 Mon Sep 17 00:00:00 2001
From: "R. David Murray" <rdmurray@bitdance.com>
Date: Tue, 23 Feb 2010 22:57:58 +0000
Subject: [PATCH] Merged revisions 78384 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk

........
  r78384 | dirkjan.ochtman | 2010-02-23 16:09:52 -0500 (Tue, 23 Feb 2010) | 4 lines

  Fix #1537721: add writeheader() method to csv.DictWriter.

  Reviewed by skip.montanaro and thomas.wouters.
........
---
 Doc/library/csv.rst  | 10 ++++++++++
 Lib/csv.py           |  4 ++++
 Lib/test/test_csv.py |  4 ++++
 Misc/NEWS            |  2 ++
 4 files changed, 20 insertions(+)

diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
index 510d35a4000..502d9349dbf 100644
--- a/Doc/library/csv.rst
+++ b/Doc/library/csv.rst
@@ -392,6 +392,16 @@ Writer objects have the following public attribute:
    A read-only description of the dialect in use by the writer.
 
 
+DictWriter objects have the following public method:
+
+
+.. method:: DictWriter.writeheader()
+
+   Write a row with the field names (as specified in the constructor).
+
+   .. versionadded:: 2.7
+
+
 .. _csv-examples:
 
 Examples
diff --git a/Lib/csv.py b/Lib/csv.py
index 59ec372ec0a..5ae5a730468 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -127,6 +127,10 @@ class DictWriter:
         self.extrasaction = extrasaction
         self.writer = writer(f, dialect, *args, **kwds)
 
+    def writeheader(self):
+        header = dict(zip(self.fieldnames, self.fieldnames))
+        self.writerow(header)
+
     def _dict_to_list(self, rowdict):
         if self.extrasaction == "raise":
             wrong_fields = [k for k in rowdict if k not in self.fieldnames]
diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 29e54f789a0..2c4b78305df 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -535,8 +535,12 @@ class TestDictFields(unittest.TestCase):
     def test_write_simple_dict(self):
         with TemporaryFile("w+", newline='') as fileobj:
             writer = csv.DictWriter(fileobj, fieldnames = ["f1", "f2", "f3"])
+            writer.writeheader()
+            fileobj.seek(0)
+            self.assertEqual(fileobj.readline(), "f1,f2,f3\r\n")
             writer.writerow({"f1": 10, "f3": "abc"})
             fileobj.seek(0)
+            fileobj.readline() # header
             self.assertEqual(fileobj.read(), "10,,abc\r\n")
 
     def test_write_no_fields(self):
diff --git a/Misc/NEWS b/Misc/NEWS
index 6abe1e2c93e..666139f104f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -254,6 +254,8 @@ C-API
 Library
 -------
 
+- Issue #1537721: Add a writeheader() method to csv.DictWriter.
+
 - Issue #7959: ctypes callback functions are now registered correctly
   with the cylce garbage collector.