1 files changed, 22 insertions, 0 deletions
diff --git a/argparse_utils.py b/argparse_utils.py
index 0ee2be9..2d2297c 100644
--- a/argparse_utils.py
+++ b/argparse_utils.py
@@ -232,6 +232,28 @@ def valid_datetime(txt: str) -> datetime.datetime:
     raise argparse.ArgumentTypeError(msg)
 
 
+def valid_duration(txt: str) -> datetime.timedelta:
+    """If the string is a valid time duration, return a
+    datetime.timedelta representing the period of time.  Otherwise
+    maybe raise an ArgumentTypeError or potentially just treat the
+    time window as zero in length.
+
+    >>> valid_duration('3m')
+    datetime.timedelta(seconds=180)
+
+    >>> valid_duration('your mom')
+    datetime.timedelta(seconds=0)
+
+    """
+    from datetime_utils import parse_duration
+    try:
+        secs = parse_duration(txt)
+    except Exception as e:
+        raise argparse.ArgumentTypeError(e)
+    finally:
+        return datetime.timedelta(seconds=secs)
+
+
 if __name__ == '__main__':
     import doctest
     doctest.ELLIPSIS_MARKER = '-ANYTHING-'