ch11-24: clean up by @eumiro & sync with Atlas

19-coroutine/coroaverager2.py

@@ -0,0 +1,61 @@
+"""
+A coroutine to compute a running average.
+
+Testing ``averager`` by itself::
+
+# tag::RETURNING_AVERAGER_DEMO1[]
+
+    >>> coro_avg = averager()
+    >>> next(coro_avg)
+    >>> coro_avg.send(10)  # <1>
+    >>> coro_avg.send(30)
+    >>> coro_avg.send(6.5)
+    >>> coro_avg.send(None)  # <2>
+    Traceback (most recent call last):
+       ...
+    StopIteration: Result(count=3, average=15.5)
+
+# end::RETURNING_AVERAGER_DEMO1[]
+
+Catching `StopIteration` to extract the value returned by
+the coroutine::
+
+# tag::RETURNING_AVERAGER_DEMO2[]
+
+    >>> coro_avg = averager()
+    >>> next(coro_avg)
+    >>> coro_avg.send(10)
+    >>> coro_avg.send(30)
+    >>> coro_avg.send(6.5)
+    >>> try:
+    ...     coro_avg.send(None)
+    ... except StopIteration as exc:
+    ...     result = exc.value
+    ...
+    >>> result
+    Result(count=3, average=15.5)
+
+# end::RETURNING_AVERAGER_DEMO2[]
+
+
+"""
+
+# tag::RETURNING_AVERAGER[]
+from collections import namedtuple
+
+Result = namedtuple('Result', 'count average')
+
+
+def averager():
+    total = 0.0
+    count = 0
+    average = None
+    while True:
+        term = yield
+        if term is None:
+            break  # <1>
+        total += term
+        count += 1
+        average = total/count
+    return Result(count, average)  # <2>
+# end::RETURNING_AVERAGER[]