Fix #1537721: add writeheader() method to csv.DictWriter.
Reviewed by skip.montanaro and thomas.wouters.
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@ -424,6 +424,16 @@ Writer objects have the following public attribute:
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A read-only description of the dialect in use by the writer.
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DictWriter objects have the following public method:
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.. method:: DictWriter.writeheader()
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Write a row with the field names (as specified in the constructor).
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.. versionadded:: 2.7
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.. _csv-examples:
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Examples
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@ -132,6 +132,10 @@ class DictWriter:
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self.extrasaction = extrasaction
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self.writer = writer(f, dialect, *args, **kwds)
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def writeheader(self):
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header = dict(zip(self.fieldnames, self.fieldnames))
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self.writerow(header)
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def _dict_to_list(self, rowdict):
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if self.extrasaction == "raise":
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wrong_fields = [k for k in rowdict if k not in self.fieldnames]
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@ -598,8 +598,12 @@ class TestDictFields(unittest.TestCase):
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fileobj = os.fdopen(fd, "w+b")
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try:
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writer = csv.DictWriter(fileobj, fieldnames = ["f1", "f2", "f3"])
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writer.writeheader()
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fileobj.seek(0)
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self.assertEqual(fileobj.readline(), "f1,f2,f3\r\n")
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writer.writerow({"f1": 10, "f3": "abc"})
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fileobj.seek(0)
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fileobj.readline() # header
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self.assertEqual(fileobj.read(), "10,,abc\r\n")
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finally:
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fileobj.close()
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