[[2021-06-20_Sun]] #python
```python
def time_range_from_args(args):
...
else:
raise ValueError("args.duration is invalid format")
```
```python
try:
start, end = time_range_from_args(args)
except ValueError:
parser.print_help()
exit(-1)
```
[Which exception should I raise on bad/illegal argument combinations in Python? - Stack Overflow](https://stackoverflow.com/questions/256222/which-exception-should-i-raise-on-bad-illegal-argument-combinations-in-python)