import importlib


def exists(val):
    return val is not None


def get_obj_from_str(string, reload=False):
    module, cls = string.rsplit('.', 1)
    if reload:
        module_imp = importlib.import_module(module)
        importlib.reload(module_imp)
    return getattr(importlib.import_module(module, package=None), cls)


def instantiate_from_config(config):
    if "target" not in config:
        raise KeyError("Expected key `target` in config")
    return get_obj_from_str(config["target"])(**config.get("params", dict()))