source: publico/il.spdo/trunk/Paste-1.7.5.1-py2.6.egg/paste/util/import_string.py @ 5327

Última Alteração nesse arquivo desde 5327 foi 5327, incluída por fabianosantos, 8 anos atrás

Import inicial.

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1# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
2# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
3
4"""
5'imports' a string -- converts a string to a Python object, importing
6any necessary modules and evaluating the expression.  Everything
7before the : in an import expression is the module path; everything
8after is an expression to be evaluated in the namespace of that
9module.
10
11Alternately, if no : is present, then import the modules and get the
12attributes as necessary.  Arbitrary expressions are not allowed in
13that case.
14"""
15
16def eval_import(s):
17    """
18    Import a module, or import an object from a module.
19
20    A module name like ``foo.bar:baz()`` can be used, where
21    ``foo.bar`` is the module, and ``baz()`` is an expression
22    evaluated in the context of that module.  Note this is not safe on
23    arbitrary strings because of the eval.
24    """
25    if ':' not in s:
26        return simple_import(s)
27    module_name, expr = s.split(':', 1)
28    module = import_module(module_name)
29    obj = eval(expr, module.__dict__)
30    return obj
31
32def simple_import(s):
33    """
34    Import a module, or import an object from a module.
35
36    A name like ``foo.bar.baz`` can be a module ``foo.bar.baz`` or a
37    module ``foo.bar`` with an object ``baz`` in it, or a module
38    ``foo`` with an object ``bar`` with an attribute ``baz``.
39    """
40    parts = s.split('.')
41    module = import_module(parts[0])
42    name = parts[0]
43    parts = parts[1:]
44    last_import_error = None
45    while parts:
46        name += '.' + parts[0]
47        try:
48            module = import_module(name)
49            parts = parts[1:]
50        except ImportError, e:
51            last_import_error = e
52            break
53    obj = module
54    while parts:
55        try:
56            obj = getattr(module, parts[0])
57        except AttributeError:
58            raise ImportError(
59                "Cannot find %s in module %r (stopped importing modules with error %s)" % (parts[0], module, last_import_error))
60        parts = parts[1:]
61    return obj
62
63def import_module(s):
64    """
65    Import a module.
66    """
67    mod = __import__(s)
68    parts = s.split('.')
69    for part in parts[1:]:
70        mod = getattr(mod, part)
71    return mod
72
73def try_import_module(module_name):
74    """
75    Imports a module, but catches import errors.  Only catches errors
76    when that module doesn't exist; if that module itself has an
77    import error it will still get raised.  Returns None if the module
78    doesn't exist.
79    """
80    try:
81        return import_module(module_name)
82    except ImportError, e:
83        if not getattr(e, 'args', None):
84            raise
85        desc = e.args[0]
86        if not desc.startswith('No module named '):
87            raise
88        desc = desc[len('No module named '):]
89        # If you import foo.bar.baz, the bad import could be any
90        # of foo.bar.baz, bar.baz, or baz; we'll test them all:
91        parts = module_name.split('.')
92        for i in range(len(parts)):
93            if desc == '.'.join(parts[i:]):
94                return None
95        raise
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