files for chapter 18B - async/await

18b-async-await/spinner_thread.py

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+# spinner_thread.py
+
+# credits: Adapted from Michele Simionato's
+# multiprocessing example in the python-list:
+# https://mail.python.org/pipermail/python-list/2009-February/538048.html
+
+# BEGIN SPINNER_THREAD
+import threading
+import itertools
+import time
+import sys
+
+
+class Signal:  # <1>
+    go = True
+
+
+def spin(msg, signal):  # <2>
+    write, flush = sys.stdout.write, sys.stdout.flush
+    for char in itertools.cycle('|/-\\'):  # <3>
+        status = char + ' ' + msg
+        write(status)
+        flush()
+        write('\x08' * len(status))  # <4>
+        time.sleep(.1)
+        if not signal.go:  # <5>
+            break
+    write(' ' * len(status) + '\x08' * len(status))  # <6>
+
+
+def slow_function():  # <7>
+    # pretend waiting a long time for I/O
+    time.sleep(3)  # <8>
+    return 42
+
+
+def supervisor():  # <9>
+    signal = Signal()
+    spinner = threading.Thread(target=spin,
+                               args=('thinking!', signal))
+    print('spinner object:', spinner)  # <10>
+    spinner.start()  # <11>
+    result = slow_function()  # <12>
+    signal.go = False  # <13>
+    spinner.join()  # <14>
+    return result
+
+
+def main():
+    result = supervisor()  # <15>
+    print('Answer:', result)
+
+
+if __name__ == '__main__':
+    main()
+# END SPINNER_THREAD