Fix #1537721: add writeheader() method to csv.DictWriter.
Reviewed by skip.montanaro and thomas.wouters.
diff --git a/Lib/csv.py b/Lib/csv.py
index 3db5dac..1df5062 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -132,6 +132,10 @@
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 196d18c..7eef4c0 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -598,8 +598,12 @@
fileobj = os.fdopen(fd, "w+b")
try:
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")
finally:
fileobj.close()