/circuits/core/loader.py

 1# Package:  loader
 2# Date:     16th March 2011
 3# Author:   James Mills, jamesmills at comops dot com dot au
 4
 5"""
 6This module implements a generic Loader suitable for dynamically loading
 7components from other modules. This supports loading from local paths,
 8eggs and zip archives. Both setuptools and distribute are fully supported.
 9"""
10
11import sys
12from inspect import getmembers, getmodule, isclass
13
14from .handlers import handler
15from .utils import safeimport
16from .components import BaseComponent
17
18
19class Loader(BaseComponent):
20    """Create a new Loader Component
21
22    Creates a new Loader Component that enables dynamic loading of
23    components from modules either in local paths, eggs or zip archives.
24    """
25
26    channel = "loader"
27
28    def __init__(self, auto_register=True, init_args=None,
29                 init_kwargs=None, paths=None, channel=channel):
30        "initializes x; see x.__class__.__doc__ for signature"
31
32        super(Loader, self).__init__(channel=channel)
33
34        self._auto_register = auto_register
35        self._init_args = init_args or tuple()
36        self._init_kwargs = init_kwargs or dict()
37
38        if paths:
39            for path in paths:
40                sys.path.insert(0, path)
41
42    @handler("load")
43    def load(self, name):
44        module = safeimport(name)
45        if module is not None:
46
47            test = lambda x: isclass(x) \
48                and issubclass(x, BaseComponent) \
49                and getmodule(x) is module
50            components = [x[1] for x in getmembers(module, test)]
51
52            if components:
53                TheComponent = components[0]
54
55                component = TheComponent(
56                    *self._init_args,
57                    **self._init_kwargs
58                )
59
60                if self._auto_register:
61                    component.register(self)
62
63                return component