Implement Item.deepcopy()

docs/topics/items.rst

@@ -40,6 +40,7 @@ objects. Here is an example::
         name = scrapy.Field()
         price = scrapy.Field()
         stock = scrapy.Field()
+        tags = scrapy.Field()
         last_updated = scrapy.Field(serializer=str)
 
 .. note:: Those familiar with `Django`_ will notice that Scrapy Items are
@@ -158,16 +159,6 @@ To access all populated values, just use the typical `dict API`_::
 Other common tasks
 ------------------
 
-Copying items::
-
-    >>> product2 = Product(product)
-    >>> print(product2)
-    Product(name='Desktop PC', price=1000)
-
-    >>> product3 = product2.copy()
-    >>> print(product3)
-    Product(name='Desktop PC', price=1000)
-
 Creating dicts from items::
 
     >>> dict(product) # create a dict from all populated values
@@ -183,6 +174,33 @@ Creating items from dicts::
         ...
     KeyError: 'Product does not support field: lala'
 
+Copying items::
+
+    >>> product['tags'] = ['tag1']
+
+    >>> product2 = Product(product)
+    >>> print(product2)
+    Product(name='Desktop PC', price=1000, tags=['tag1'])
+
+    >>> product3 = product.copy()
+    >>> print(product3)
+    Product(name='Desktop PC', price=1000, tags=['tag1'])
+
+    >>> product4 = product.deepcopy()
+    >>> print(product4)
+    Product(name='Desktop PC', price=1000, tags=['tag1'])
+
+    >>> product['tags'].append('tag2')
+
+    >>> print(product2)
+    Product(name='Desktop PC', price=1000, tags=['tag1', 'tag2'])
+
+    >>> print(product3)
+    Product(name='Desktop PC', price=1000, tags=['tag1', 'tag2'])
+
+    >>> print(product4)
+    Product(name='Desktop PC', price=1000, tags=['tag1'])
+
 Extending Items
 ===============
 

scrapy/item.py

@@ -6,6 +6,7 @@
 
 from pprint import pformat
 from collections import MutableMapping
+from copy import deepcopy
 
 from abc import ABCMeta
 import six
@@ -96,6 +97,13 @@ def __repr__(self):
     def copy(self):
         return self.__class__(self)
 
+    def deepcopy(self):
+        """Returns a `deep copy`_ of this item.
+
+        .. _deep copy: https://docs.python.org/library/copy.html#copy.deepcopy
+        """
+        return deepcopy(self)
+
 
 @six.add_metaclass(ItemMeta)
 class Item(DictItem):

tests/test_item.py

@@ -249,6 +249,14 @@ class TestItem(Item):
         copied_item['name'] = copied_item['name'].upper()
         self.assertNotEqual(item['name'], copied_item['name'])
 
+    def test_deepcopy(self):
+        class TestItem(Item):
+            tags = Field()
+        item = TestItem({'tags': ['tag1']})
+        copied_item = item.deepcopy()
+        item['tags'].append('tag2')
+        assert item['tags'] != copied_item['tags']
+
 
 class ItemMetaTest(unittest.TestCase):