python argparse add_argument_group required

Question

In this question argparse: require either of two arguments I find a reference to the solution I want, but it isn't right. I need at least 1 of 2 options to be present, option1, option2 or both... The add_argument_group function doesn't have a required argument. The add_mutually_exclusive function has it, but it forces me to choose between the 2 options, which is not what I want. rds,

Accepted Answer

`argument_group` just controls the help display. It does not affect the parsing or check for errors. `mutually_exclusive_group` affects usage display and tests for occurrence, but as you note, its logic is not what you want.

There is a Python bug issue requesting some form of nested 'inclusive' group. But a general form that allows nesting and all versions of and/or/xor logic is not a trivial addition.

I think your simplest solution is to test the `args` after parsing. If there is a wrong mix of defaults, then raise an error.

Assuming the default for both arguments is `None`:

```
if args.option1 is None and args.option2 is None:
    parser.error('at least one of option1 and option2 is required')
```

What would be meaningful usage line? `required mutually exclusive' uses`(opt1 | opt2)`.`(opt1 & opt2)`might indicate that both are required. Your case is a`non-exclusive or`

```
usage: PROG [-h] (--opt1 OPT1 ? --opt2 OPT2)
```

python argparse add_argument_group required

Solution

Problem