Add sched example code

Author: gjbex

source-code/sched/README.md

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+# Sched
+
+Sometimes it can be useful to run functions at certain moments in time,
+similar to what cron does on Linux operatring systems.
+
+## What is it?
+
+* `cron.py`: example script using `schedule` that runs two tasks, one
+    printing the time, and a computed value, the other updating the
+    value to be printed.  The first is scheduled every 2 seconds, the
+    other every second.

source-code/sched/cron.py

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+#!/usr/bin/env python
+
+import schedule
+import time
+
+
+def print_event(event):
+    time_str = time.strftime('%Y-%m-%d %H:%M:%S', time.localtime())
+    print('{0}: {1}'.format(time_str, event['counter']))
+
+
+def set_event(event):
+    event['counter'] += 1
+
+if __name__ == '__main__':
+    event = {'counter': 0}
+    schedule.every(2).seconds.do(print_event, event)
+    schedule.every().seconds.do(set_event, event)
+    while True:
+        schedule.run_pending()
+        time.sleep(0.5)