From fce5ff1e18b522cf52379934a6560583d840e7f9 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?R=C3=A9mi=20Lapeyre?= Date: Fri, 10 May 2019 03:50:11 +0200 Subject: bpo-27497: Add return value to csv.DictWriter.writeheader (GH-12306) csv.DictWriter.writeheader() now returns the return value of the underlying csv.Writer.writerow() method. Patch contributed by Ashish Nitin Patil. --- Doc/library/csv.rst | 10 ++++++++-- Lib/csv.py | 2 +- Lib/test/test_csv.py | 6 ++++++ .../next/Library/2019-03-13-10-57-41.bpo-27497.JDmIe_.rst | 3 +++ 4 files changed, 18 insertions(+), 3 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2019-03-13-10-57-41.bpo-27497.JDmIe_.rst diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst index 17534fc..49e22fa 100644 --- a/Doc/library/csv.rst +++ b/Doc/library/csv.rst @@ -443,7 +443,8 @@ read CSV files (assuming they support complex numbers at all). .. method:: csvwriter.writerow(row) Write the *row* parameter to the writer's file object, formatted according to - the current dialect. + the current dialect. Return the return value of the call to the *write* method + of the underlying file object. .. versionchanged:: 3.5 Added support of arbitrary iterables. @@ -467,9 +468,14 @@ DictWriter objects have the following public method: .. method:: DictWriter.writeheader() - Write a row with the field names (as specified in the constructor). + Write a row with the field names (as specified in the constructor) to + the writer's file object, formatted according to the current dialect. Return + the return value of the :meth:`csvwriter.writerow` call used internally. .. versionadded:: 3.2 + .. versionchanged:: 3.8 + :meth:`writeheader` now also returns the value returned by + the :meth:`csvwriter.writerow` method it uses internally. .. _csv-examples: diff --git a/Lib/csv.py b/Lib/csv.py index eeeedab..dc85077 100644 --- a/Lib/csv.py +++ b/Lib/csv.py @@ -140,7 +140,7 @@ class DictWriter: def writeheader(self): header = dict(zip(self.fieldnames, self.fieldnames)) - self.writerow(header) + return self.writerow(header) def _dict_to_list(self, rowdict): if self.extrasaction == "raise": diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py index 7a33313..a16d140 100644 --- a/Lib/test/test_csv.py +++ b/Lib/test/test_csv.py @@ -608,6 +608,12 @@ class TestQuotedEscapedExcel(TestCsvBase): class TestDictFields(unittest.TestCase): ### "long" means the row is longer than the number of fieldnames ### "short" means there are fewer elements in the row than fieldnames + def test_writeheader_return_value(self): + with TemporaryFile("w+", newline='') as fileobj: + writer = csv.DictWriter(fileobj, fieldnames = ["f1", "f2", "f3"]) + writeheader_return_value = writer.writeheader() + self.assertEqual(writeheader_return_value, 10) + def test_write_simple_dict(self): with TemporaryFile("w+", newline='') as fileobj: writer = csv.DictWriter(fileobj, fieldnames = ["f1", "f2", "f3"]) diff --git a/Misc/NEWS.d/next/Library/2019-03-13-10-57-41.bpo-27497.JDmIe_.rst b/Misc/NEWS.d/next/Library/2019-03-13-10-57-41.bpo-27497.JDmIe_.rst new file mode 100644 index 0000000..f6da114 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2019-03-13-10-57-41.bpo-27497.JDmIe_.rst @@ -0,0 +1,3 @@ +:meth:`csv.DictWriter.writeheader` now returns the return value of the +underlying :meth:`csv.Writer.writerow` method. Patch contributed by Ashish +Nitin Patil. -- cgit v0.12