added join_multivalued parameter to CsvItemExporter

docs/topics/exporters.rst

@@ -264,7 +264,7 @@ XmlItemExporter
 CsvItemExporter
 ---------------
 
-.. class:: CsvItemExporter(file, include_headers_line=True, \**kwargs)
+.. class:: CsvItemExporter(file, include_headers_line=True, join_multivalued=',', \**kwargs)
 
    Exports Items in CSV format to the given file-like object. If the
    :attr:`fields_to_export` attribute is set, it will be used to define the
@@ -278,6 +278,10 @@ CsvItemExporter
       :attr:`BaseItemExporter.fields_to_export` or the first exported item fields.
    :type include_headers_line: boolean
 
+   :param join_multivalued: The char (or chars) that will be used for joining
+      multi-valued fields, if found.
+   :type include_headers_line: str
+
    The additional keyword arguments of this constructor are passed to the
    :class:`BaseItemExporter` constructor, and the leftover arguments to the
    `csv.writer`_ constructor, so you can use any `csv.writer` constructor

scrapy/contrib/exporter/__init__.py

@@ -143,11 +143,20 @@ class XmlItemExporter(BaseItemExporter):
 
 class CsvItemExporter(BaseItemExporter):
 
-    def __init__(self, file, include_headers_line=True, **kwargs):
+    def __init__(self, file, include_headers_line=True, join_multivalued=',', **kwargs):
         self._configure(kwargs, dont_fail=True)
         self.include_headers_line = include_headers_line
         self.csv_writer = csv.writer(file, **kwargs)
         self._headers_not_written = True
+        self._join_multivalued = join_multivalued
+
+    def _to_str_if_unicode(self, value):
+        if isinstance(value, (list, tuple)):
+            try:
+                value = self._join_multivalued.join(value)
+            except TypeError: # list in value may not contain strings
+                pass
+        return super(CsvItemExporter, self)._to_str_if_unicode(value)
 
     def export_item(self, item):
         if self._headers_not_written:

scrapy/tests/test_contrib_exporter.py

@@ -127,6 +127,18 @@ class CsvItemExporterTest(BaseItemExporterTest):
         ie.finish_exporting()
         self.assertEqual(output.getvalue(), '22,John\xc2\xa3\r\n')
 
+    def test_join_multivalue(self):
+        class TestItem2(Item):
+            name = Field()
+            friends = Field()
+
+        i = TestItem2(name='John', friends=['Mary', 'Paul'])
+        output = StringIO()
+        ie = CsvItemExporter(output, include_headers_line=False)
+        ie.start_exporting()
+        ie.export_item(i)
+        ie.finish_exporting()
+        self.assertEqual(output.getvalue(), '"Mary,Paul",John\r\n')
 
 class XmlItemExporterTest(BaseItemExporterTest):