update from Atlas with major reorg

20-descriptor/method_is_descriptor.py

@@ -0,0 +1,41 @@
+"""
+# BEGIN FUNC_DESCRIPTOR_DEMO
+
+    >>> word = Text('forward')
+    >>> word  # <1>
+    Text('forward')
+    >>> word.reverse()  # <2>
+    Text('drawrof')
+    >>> Text.reverse(Text('backward'))  # <3>
+    Text('drawkcab')
+    >>> type(Text.reverse), type(word.reverse)  # <4>
+    (<class 'function'>, <class 'method'>)
+    >>> list(map(Text.reverse, ['repaid', (10, 20, 30), Text('stressed')]))  # <5>
+    ['diaper', (30, 20, 10), Text('desserts')]
+    >>> Text.reverse.__get__(word)  # <6>
+    <bound method Text.reverse of Text('forward')>
+    >>> Text.reverse.__get__(None, Text)  # <7>
+    <function Text.reverse at 0x101244e18>
+    >>> word.reverse  # <8>
+    <bound method Text.reverse of Text('forward')>
+    >>> word.reverse.__self__  # <9>
+    Text('forward')
+    >>> word.reverse.__func__ is Text.reverse  # <10>
+    True
+
+# END FUNC_DESCRIPTOR_DEMO
+"""
+
+# BEGIN FUNC_DESCRIPTOR_EX
+import collections
+
+
+class Text(collections.UserString):
+
+    def __repr__(self):
+        return 'Text({!r})'.format(self.data)
+
+    def reverse(self):
+        return self[::-1]
+
+# END FUNC_DESCRIPTOR_EX