updated more ch. 18 examples to Python 3.7

Author: ramalho

18-asyncio-py3.7/countdown.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+# Inspired by
+# https://snarky.ca/how-the-heck-does-async-await-work-in-python-3-5/
+
+import asyncio
+import time
+
+
+async def countdown(label, delay):
+    tabs = (ord(label) - ord('A')) * '\t'
+    n = 3
+    while n > 0:
+        await asyncio.sleep(delay)  # <----
+        dt = time.perf_counter() - t0
+        print('━' * 50)
+        print(f'{dt:7.4f}s \t{tabs}{label} = {n}')
+        n -= 1
+
+loop = asyncio.get_event_loop()
+tasks = [
+    loop.create_task(countdown('A', .7)),
+    loop.create_task(countdown('B', 2)),
+    loop.create_task(countdown('C', .3)),
+    loop.create_task(countdown('D', 1)),
+]
+t0 = time.perf_counter()
+loop.run_until_complete(asyncio.wait(tasks))
+loop.close()
+print('━' * 50)

18-asyncio-py3.7/spinner_asyncio.py

@@ -1,10 +1,12 @@
-# spinner_await.py
+#!/usr/bin/env python3
+
+# spinner_asyncio.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
 
-# BEGIN SPINNER_AWAIT
+# BEGIN SPINNER_ASYNCIO
 import asyncio
 import itertools
 import sys
@@ -18,31 +20,31 @@ async def spin(msg):  # <1>
         flush()
         write('\x08' * len(status))
         try:
-            await asyncio.sleep(.1)  # <3>
-        except asyncio.CancelledError:  # <4>
+            await asyncio.sleep(.1)  # <2>
+        except asyncio.CancelledError:  # <3>
             break
     write(' ' * len(status) + '\x08' * len(status))
 
 
-async def slow_function():  # <5>
+async def slow_function():  # <4>
     # pretend waiting a long time for I/O
-    await asyncio.sleep(3)  # <6>
+    await asyncio.sleep(3)  # <5>
     return 42
 
 
-async def supervisor():  # <7>
-    spinner = asyncio.create_task(spin('thinking!'))  # <8>
-    print('spinner object:', spinner)  # <9>
-    result = await slow_function()  # <10>
-    spinner.cancel()  # <11>
+async def supervisor():  # <6>
+    spinner = asyncio.create_task(spin('thinking!'))  # <7>
+    print('spinner object:', spinner)  # <8>
+    result = await slow_function()  # <9>
+    spinner.cancel()  # <10>
     return result
 
 
 def main():
-    result = asyncio.run(supervisor())  # <12>
+    result = asyncio.run(supervisor())  # <11>
     print('Answer:', result)
 
 
 if __name__ == '__main__':
     main()
-# END SPINNER_AWAIT
+# END SPINNER_ASYNCIO

18-asyncio-py3.7/spinner_curio.py

@@ -1,3 +1,5 @@
+#!/usr/bin/env python3
+
 # spinner_thread.py
 
 # credits: Adapted from Michele Simionato's