PY3 port flatten and iflatten

scrapy/utils/python.py

@@ -23,8 +23,12 @@ def flatten(x):
     >>> [1, 2, [3,4], (5,6)]
     [1, 2, [3, 4], (5, 6)]
     >>> flatten([[[1,2,3], (42,None)], [4,5], [6], 7, (8,9,10)])
-    [1, 2, 3, 42, None, 4, 5, 6, 7, 8, 9, 10]"""
-
+    [1, 2, 3, 42, None, 4, 5, 6, 7, 8, 9, 10]
+    >>> flatten(["foo", "bar"])
+    ['foo', 'bar']
+    >>> flatten(["foo", ["baz", 42], "bar"])
+    ['foo', 'baz', 42, 'bar']
+    """
     return list(iflatten(x))
 
 
@@ -32,15 +36,38 @@ def iflatten(x):
     """iflatten(sequence) -> iterator
 
     Similar to ``.flatten()``, but returns iterator instead"""
-
     for el in x:
-        if hasattr(el, "__iter__"):
+        if is_listlike(el):
             for el_ in flatten(el):
                 yield el_
         else:
             yield el
 
 
+def is_listlike(x):
+    """
+    >>> is_listlike("foo")
+    False
+    >>> is_listlike(5)
+    False
+    >>> is_listlike(b"foo")
+    False
+    >>> is_listlike([b"foo"])
+    True
+    >>> is_listlike((b"foo",))
+    True
+    >>> is_listlike({})
+    True
+    >>> is_listlike(set())
+    True
+    >>> is_listlike((x for x in range(3)))
+    True
+    >>> is_listlike(six.moves.xrange(5))
+    True
+    """
+    return hasattr(x, "__iter__") and not isinstance(x, (six.text_type, bytes))
+
+
 def unique(list_, key=lambda x: x):
     """efficient function to uniquify a list preserving item order"""
     seen = set()