Python 动态类名

Question

可能的重复：
Python模块的动态加载
python：如何动态向类添加属性？

我有一个包含文件名和类名的字典，如何导入此类名称以及如何创建此类？

示例：

classNames = { 'MCTest':MCTestClass}

我想导入 MCTest 并创建 MCTestClass。

Answer 1

您必须使用 __import__ 函数：

http://docs. python.org/library/functions.html#import

来自文档页面的示例：

>>> import sys
>>> name = 'foo.bar.baz'
>>> __import__(name)
<module 'foo' from ...>
>>> baz = sys.modules[name]
>>> baz
<module 'foo.bar.baz' from ...>

要从 baz 实例化一个类，您应该能够执行以下操作：

>>> SomeClass = getattr(baz, 'SomeClass')
>>> obj = SomeClass()

Answer 2

来自turbogears.util：

def load_class(dottedpath):
    """Load a class from a module in dotted-path notation.

    E.g.: load_class("package.module.class").

    Based on recipe 16.3 from Python Cookbook, 2ed., by Alex Martelli,
    Anna Martelli Ravenscroft, and David Ascher (O'Reilly Media, 2005)

    """
    assert dottedpath is not None, "dottedpath must not be None"
    splitted_path = dottedpath.split('.')
    modulename = '.'.join(splitted_path[:-1])
    classname = splitted_path[-1]
    try:
        try:
            module = __import__(modulename, globals(), locals(), [classname])
        except ValueError: # Py < 2.5
            if not modulename:
                module = __import__(__name__.split('.')[0],
                    globals(), locals(), [classname])
    except ImportError:
        # properly log the exception information and return None
        # to tell caller we did not succeed
        logging.exception('tg.utils: Could not import %s'
            ' because an exception occurred', dottedpath)
        return None
    try:
        return getattr(module, classname)
    except AttributeError:
        logging.exception('tg.utils: Could not import %s'
            ' because the class was not found', dottedpath)
        return None

像这样使用它：

cls = load_class('package.module.class')
obj = cls(...)