#!/usr/bin/env python3
# coding: utf-8
from abc import abstractmethod, ABCMeta
from argparse import Action, ArgumentParser
from yaml import load
class SetDefaultFromFile(Action, metaclass=ABCMeta):
"""
Populates arguments with file contents.
This abstract class is to be inherited per type of file read.
"""
def __call__(self, parser, namespace, values, option_string=None):
config = self._get_config_from_file(values)
for key, value in config.items():
setattr(namespace, key, value)
@abstractmethod
def _get_config_from_file(self, filename):
raise NotImplementedError
class SetDefaultFromYAMLFile(SetDefaultFromFile):
"""
Populates arguments with a YAML file contents.
"""
def _get_config_from_file(self, filename):
with open(filename) as f:
config = load(f)
return config
_TEST_FILE = 'test.yaml'
_NAME = 'spam'
_FILE_VALUE = 'eggs'
with open(_TEST_FILE, mode='w') as f:
f.write('{}: {}'.format(_NAME, _FILE_VALUE))
_PARSER = ArgumentParser()
_PARSER.add_argument('--config', action=SetDefaultFromYAMLFile)
_PARSER.add_argument('--{}'.format(_NAME))
def test_file_content_populates_args():
args = _PARSER.parse_args('--config {}'.format(_TEST_FILE).split())
assert getattr(args, _NAME) == _FILE_VALUE
def test_file_content_is_erased_if_arg_given_after():
expected = '42'
args = _PARSER.parse_args('--config {} --spam {}'.format(_TEST_FILE,
expected).split())
assert getattr(args, _NAME) == expected
def test_arg_is_erases_if_file_is_given_after():
value = 12
args = _PARSER.parse_args('--spam {} --config {}'.format(value,
_TEST_FILE).split())
assert getattr(args, _NAME) == _FILE_VALUE
