Getting full path from the relative path with Argparse

Question

I am writing a small command line utility for my script and I can't figure out how to properly get the full path from the argument.

Here's what I mean.

parser = ArgumentParser()
parser.add_argument("-src",
                    required = True, help="path to some folder")
args = parser.parse_args()
print(args.src)

If the user pass the full path, e.g. "/home/username/projectname/folder", everything is fine.

But if the user runs the script from let's say "projectname" folder and pass the relative path "./folder" I get exactly the same string "./folder" while parsing the arguments instead of the full path "/home/username/projectname/folder".

So, I have been wondering if there is some kind of inbuilt functionality in Argparse that allows to get the full path from the relative path?

Answer 1

To add onto Tryph's answer, you can specify the type parameter in the argument declaration. It can take any callable that takes a single string argument and returns the converted value:

parser.add_argument("-src",
                    required=True,
                    help="path to some folder",
                    type=os.path.abspath)

This returns a string with the absolute path, you could specify your own function as well:

def my_full_path(string):
    script_dir = os.path.dirname(__file__)
    return  os.path.normpath(os.path.join(script_dir, string))


parser = ArgumentParser()
parser.add_argument("-src",
                    required=True,
                    help="path to some folder",
                    type=my_full_path)

Answer 2

EDIT: The Alex's answer shows how to make argparse manage relative-to-absolute path conversion by simply filling the add_argument's type parameter.

---

I do not think argparse provides such feature but you can achieve it using os.path.abspath:

abs_src = os.path.abspath(args.src)

Keep in mind that this will make an absolute path by concatenating the working directory with the relative path. Thus the path is considered relative to working directory.

---

If you want to make the path relative to the script directory, you can use os.path.dirname on the __file__ variable and os.path.join to build an absolute path from a path relative to your Python script:

script_dir = os.path.dirname(__file__)
abs_src = os.path.join(script_dir, args.src)

Finally, since joined path can contain tokens such as . and .., you can "prettify" your built path with os.path.normpath:

abs_path = os.path.normpath(os.path.join(script_dir, args.src))