def test_dictwriter_append_header_only(): fileobj = StringIO() writer1 = DictWriter(fileobj, fieldnames=["f1", "f2", "f3"]) writer1.writeheader() assert fileobj.getvalue() == "f1,f2,f3\r\n" writer2 = DictWriter.append(fileobj) writer2.writerow({"f1": 2, "f2": 5, "f3": "xyz"}) assert fileobj.getvalue() == "f1,f2,f3\r\n2,5,xyz\r\n"
def test_dictwriter_append_empty(): fileobj = StringIO() with pytest.raises(ValueError): writer = DictWriter.append(fileobj)