利用 __import__ 方法实现 Python 模型的懒加载

laszyimport.py

class LazyImport:
    def __init__(self, module_name):
        self.module_name = module_name
        self.module = None

    def __getattr__(self, name):
        if self.module is None:
            self.module = __import__(self.module_name)
        return getattr(self.module, name)

string = LazyImport("string")
print string.lowercase