added cronjob decorator code

code/cron.py

@@ -0,0 +1,53 @@
+from cron_converter import Cron
+from configparser import ConfigParser
+from pathlib import Path
+from datetime import datetime
+import dateutil
+import time
+import functools
+import logging
+
+# load default values
+config = ConfigParser()
+config.read(Path(__file__).parent / 'defaults.ini')
+SCHEDULE = config.get('cron', 'schedule')
+TZ = config.get('cron', 'tz')
+
+
+def cronjob(
+    schedule: str = SCHEDULE,
+    tz: str = TZ
+):
+    """
+    decorator for running function as a cronjob.
+    """
+    logging.info(f'started cronjob with schedule {schedule} and tz {tz}')
+
+    def decorator_cronjob(func):
+        @functools.wraps(func)
+        def wrapper_cronjob(*args, **kwargs):
+            scheduler = Cron(schedule).schedule(timezone_str=tz)
+            trigger_time = scheduler.next()
+            while True:
+                while trigger_time > datetime.now(tz=dateutil.tz.gettz(tz)):
+                    # waiting loop
+                    time.sleep(1)
+                # actual execution
+                try:
+                    func(*args, **kwargs)
+                except Exception as e:
+                    logging.warning(f'failed executing {func}: {e}')
+                    raise
+                else:
+                    # update trigger time
+                    trigger_time = scheduler.next()
+        return wrapper_cronjob
+    return decorator_cronjob
+
+
+if __name__ == '__main__':
+    @cronjob(schedule='* * * * *', tz=TZ)
+    def test_loop(msg: str):
+        print(msg)
+
+    test_loop('hello world')