stevedore_plugin_interface_with_driver_loader_dynamic_loading.py

1# stevedore/example/base.py
2import abc
3
4class FormatterBase(metaclass=abc.ABCMeta):
5    """Base class for example plugin used in the tutorial."""
6
7    def __init__(self, max_width=60):
8        self.max_width = max_width
9
10    @abc.abstractmethod
11    def format(self, data):
12        """Format the data and return unicode characters.
13
14        :param data: A dictionary with string keys and values.
15        :type data: dict(str:str)
16        :returns: iterable of strings
17        """
18
19# stevedore/example/simple.py
20class Simple(FormatterBase):
21    """A very basic formatter."""
22
23    def format(self, data):
24        for name, value in sorted(data.items()):
25            line = '{name}: {value}\n'.format(
26                name=name,
27                value=value,
28            )
29            yield line
30
31# stevedore/example/load_as_driver.py
32import argparse
33from stevedore import driver
34
35if __name__ == '__main__':
36    parser = argparse.ArgumentParser()
37    parser.add_argument(
38        'format',
39        nargs='?',
40        default='simple',
41        help='the name of the output format',
42    )
43    parser.add_argument(
44        '--width',
45        default=60,
46        type=int,
47        help='the maximum width for output',
48    )
49    parsed_args = parser.parse_args()
50
51    data = {
52        'a': 'A',
53        'b': 'B',
54        'long': 'longer than a line' * 10,
55    }
56
57    mgr = driver.DriverManager(
58        namespace='stevedore.example.formatter',
59        name=parsed_args.format,
60        invoke_on_load=True,
61        invoke_args=(parsed_args.width,),
62    )
63    for chunk in mgr.driver.format(data):
64        print(chunk, end='')