updated concurrency examples

concurrency/spinner_proc.py

@@ -0,0 +1,38 @@
+# spinner_proc.py
+# credit: Example by Michele Simionato in comp lang python.
+# source:
+# http://python-3-patterns-idioms-test.readthedocs.org/en/latest/CoroutinesAndConcurrency.html
+
+import sys
+import time
+import multiprocessing
+
+DELAY = 0.1
+DISPLAY = '|/-\\'
+
+
+def spinner_func(before='', after=''):
+    write, flush = sys.stdout.write, sys.stdout.flush
+    while True:
+        for char in DISPLAY:
+            msg = '{} {} {}'.format(before, char, after)
+            write(msg)
+            flush()
+            write('\x08' * len(msg))
+            time.sleep(DELAY)
+
+
+def long_computation():
+    # emulate a long computation
+    time.sleep(3)
+
+if __name__ == '__main__':
+    spinner = multiprocessing.Process(
+        None, spinner_func, args=('Please wait ... ', ' thinking!'))
+    spinner.start()
+
+    try:
+        long_computation()
+        print('\nComputation done')
+    finally:
+        spinner.terminate()