spinner curio example in chapter 18b

Author: ramalho

18b-async-await/README.rst

@@ -1,4 +1,4 @@
-Sample code for Chapter 18 - "Concurrency with asyncio"
+Refactored sample code for Chapter 18 - "Concurrency with asyncio"
 
 From the book "Fluent Python" by Luciano Ramalho (O'Reilly, 2015)
 http://shop.oreilly.com/product/0636920032519.do

18b-async-await/spinner_curio.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+
+# spinner_curio.py
+
+# credits: Example by Luciano Ramalho inspired by
+# Michele Simionato's multiprocessing example in the python-list:
+# https://mail.python.org/pipermail/python-list/2009-February/538048.html
+
+import curio
+
+import itertools
+import sys
+
+
+async def spin(msg):  # <1>
+    write, flush = sys.stdout.write, sys.stdout.flush
+    for char in itertools.cycle('|/-\\'):
+        status = char + ' ' + msg
+        write(status)
+        flush()
+        write('\x08' * len(status))
+        try:
+            await curio.sleep(.1)  # <2>
+        except curio.CancelledError:  # <3>
+            break
+    write(' ' * len(status) + '\x08' * len(status))
+
+
+async def slow_function():  # <4>
+    # pretend waiting a long time for I/O
+    await curio.sleep(3)  # <5>
+    return 42
+
+
+async def supervisor():  # <6>
+    spinner = await curio.spawn(spin('thinking!'))  # <7>
+    print('spinner object:\n ', repr(spinner))  # <8>
+    result = await slow_function()  # <9>
+    await spinner.cancel()  # <10>
+    return result
+
+
+def main():
+    result = curio.run(supervisor)  # <12>
+    print('Answer:', result)
+
+
+if __name__ == '__main__':
+    main()