draft of coroutine examples

control/coroaverager.py

@@ -0,0 +1,45 @@
+"""
+Closing a generator raises ``GeneratorExit`` at the pending ``yield``
+
+    >>> coro_avg = averager()
+    >>> next(coro_avg)
+    0.0
+    >>> coro_avg.send(10)
+    10.0
+    >>> coro_avg.send(20)
+    15.0
+    >>> coro_avg.send(30)
+    20.0
+    >>> coro_avg.close()
+    -> total: 60.0  average: 20.0  terms: 3
+
+
+Other exceptions propagate to the caller:
+
+    >>> coro_avg = averager()
+    >>> next(coro_avg)
+    0.0
+    >>> coro_avg.send(10)
+    10.0
+    >>> coro_avg.send('spam')
+    Traceback (most recent call last):
+      ...
+    TypeError: unsupported operand type(s) for +=: 'float' and 'str'
+
+
+"""
+
+# BEGIN CORO_AVERAGER
+def averager():
+    total = average = 0.0
+    count = 0
+    try:
+        while True:
+            term = yield average
+            total += term
+            count += 1
+            average = total/count
+    except GeneratorExit:
+        msg = '-> total: {}  average: {}  terms: {}'
+        print(msg.format(total, average, count))
+# END CORO_AVERAGER