[Suggestion] Allow to reference previous arguments as default values

[Henning742]

Not a professional coder so I don't know if this suggestion is good.

What I want to accomplish: Say there're two arguments:

exp_name: str = 'your_exp_name' 
exp_dir: str = 'work_dirs/{args.exp_name}' 

then the second line means its default value is using the value of 'exp_name'.

This is my implementation:

import re
def eval_arg_strings(args):
    for k, v in args.__dict__.items():
        if isinstance(v, str):
            to_eval = re.findall(r'{args\.(.+)}', v)
            to_eval = [a for a in to_eval if hasattr(args, a)]
            for key_word in to_eval:
                real_v = getattr(args, key_word)
                assert isinstance(real_v, str)
                setattr(args, k, v.replace("{args." + key_word + "}", real_v))
    return args

Any comment is appreciated, thank you.

[martinjm97]

While the syntax youre're using is more concise, we believe that this breaks from standard convention. Tap currently supports similar functionality with process_args:

class MyTap(Tap):
    exp_name: str = 'your_exp_name' 
    exp_dir: str | None = None

    def process_args(self):
        if self.exp_dir is None:
            self.exp_dir = f'work_dirs/{self.exp_name}' 

This allows the user to optionally pass exp_dir from the command line and if no exp_dir is specified, return f'work_dirs/{self.exp_name}'

--JK