Move MutableChain to scrapy.utils.python

scrapy/core/spidermw.py

@@ -11,32 +11,13 @@ from scrapy.exceptions import _InvalidOutput
 from scrapy.middleware import MiddlewareManager
 from scrapy.utils.defer import mustbe_deferred
 from scrapy.utils.conf import build_component_list
+from scrapy.utils.python import MutableChain
 
 
 def _isiterable(possible_iterator):
     return hasattr(possible_iterator, '__iter__')
 
 
-class MutableChain:
-    """
-    Thin wrapper around itertools.chain, allowing to add iterables "in-place"
-    """
-    def __init__(self, *args):
-        self.data = chain(*args)
-
-    def extend(self, *iterables):
-        self.data = chain(self.data, *iterables)
-
-    def __iter__(self):
-        return self.data.__iter__()
-
-    def __next__(self):  # py3
-        return self.data.__next__()
-
-    def next(self):  # py2
-        return self.data.next()
-
-
 class SpiderMiddlewareManager(MiddlewareManager):
 
     component_name = 'spider middleware'

scrapy/utils/python.py

@@ -9,6 +9,7 @@ import weakref
 import errno
 import six
 from functools import partial, wraps
+from itertools import chain
 import sys
 
 from scrapy.utils.decorators import deprecated
@@ -387,3 +388,23 @@ if hasattr(sys, "pypy_version_info"):
 else:
     def garbage_collect():
         gc.collect()
+
+
+class MutableChain(object):
+    """
+    Thin wrapper around itertools.chain, allowing to add iterables "in-place"
+    """
+    def __init__(self, *args):
+        self.data = chain(*args)
+
+    def extend(self, *iterables):
+        self.data = chain(self.data, *iterables)
+
+    def __iter__(self):
+        return self.data.__iter__()
+
+    def __next__(self):  # py3
+        return self.data.__next__()
+
+    def next(self):  # py2
+        return self.data.next()