ARGPARSE-FROM-FILE

argparse-from-file is a lightweight wrapper for Python's standard argparse module. It allows your program to read default arguments from a configuration file, which are prepended to arguments provided on the command line.

The latest version of this document and code is available at https://github.com/bulletmark/argparse-from-file.

Features

• Drop-in replacement: Simply change import argparse to import argparse_from_file as argparse. No other code changes are needed for basic functionality.
• Automatic configuration: By default, it loads arguments from <program_name>-flags.conf in the user's configuration directory (e.g., ~/.config/ on Linux). The exact path is determined using the platformdirs library to respect OS conventions.
• Custom configuration file: Specify a custom file path with the from_file argument to ArgumentParser().
• Simple file format: The configuration file is a simple text file with options specified on one or more lines. Blank lines and lines starting with # are ignored.
• Informative help text: The program's help message is automatically updated to show the path to the configuration file.

Usage

To get started, replace the standard argparse import in your project:

# import argparse
import argparse_from_file as argparse

That's it! Your application will now automatically look for a default configuration file and use the default arguments provided therein.

To specify a custom configuration file, use the from_file keyword argument, which is the only addition to the standard ArgumentParser() API:

# Use a specific () file path
parser = argparse.ArgumentParser(from_file='/path/to/myprog.conf', ..)

# Use a file relative to the user's config directory
parser = argparse.ArgumentParser(from_file='myprog.conf', ..)

The from_file argument accepts a string or a pathlib.Path. Relative paths are resolved relative to the user's configuration directory as determined by platformdirs.

Configuration File Format

Arguments in the configuration file are best specified one per line so they can easily be commented out. It is also recommended to use long-form options for clarity.

Example ~/.config/myprog-flags.conf:

# Always run with foo set to 123
--foo 123

# Default to verbose output
--verbose

Customizing the Help Message

argparse-from-file automatically adds an epilog to the help message indicating the configuration file path. If you instead provide a custom epilog (or usage or description), you can embed a #FROM_FILE_PATH# placeholder, and it will be replaced with the actual path used.

Example

Here is a simple example program (myprog.py):

#!/usr/bin/python3
import argparse_from_file as argparse

parser = argparse.ArgumentParser()
parser.add_argument('--foo', type=int, default=42, help='foo help')
opts = parser.parse_args()

print(f"foo is: {opts.foo}")

If ~/.config/myprog-flags.conf contains --foo=123, the output is:

$ python myprog.py
foo is: 123

The help text (epilog) is also automatically added as seen below:

$ python myprog.py -h
usage: myprog.py [-h] [--foo FOO]

options:
  -h, --help  show this help message and exit
  --foo FOO   foo help

Note you can set default starting options in ~/.config/myprog-flags.conf.

Installation

Arch Linux users can install python-argparse-from-file from the AUR.

Alternatively, argparse-from-file is available on PyPI and can be installed with pip:

pip install argparse-from-file

License

Copyright (C) 2025 Mark Blakeney. This program is distributed under the terms of the GNU General Public License. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License at https://opensource.org/license/gpl-3-0 for more details.