函数声明返回str却提示返回Any类型，如何让类型检查工具识别正确类型？

我编写了一个读取version.py并返回版本值的函数write_ini，函数声明返回str类型，但一直收到错误提示：「Returning Any from function declared to return "str"」，尽管VERSION["VERSION"]实际是字符串类型。

函数write_ini代码： #

def write_ini() -> str:
    """Write version.ini file by extracting version from version.py."""
    # get root dirname
    filepath = realpath(__file__)
    root = dirname(dirname(dirname(filepath)))
    VERSION: Dict = {}

    # Extract version from version.py
    with open(op.join(root, "package_folder", "version.py"), encoding="utf8") as version_file:
        exec(version_file.read(), VERSION)
    print(VERSION["VERSION"])
    config["VERSION"] = {"cv_version": "v{}".format(VERSION["VERSION"])}

    # write to version.ini
    with open("version.ini", "w") as configfile:
        config.write(configfile)

    return VERSION["VERSION"]

version.py代码： #

_MAJOR = "1"
_MINOR = "0"
_REVISION = "13"

VERSION_SHORT = f"{_MAJOR}.{_MINOR}"
VERSION = f"{_MAJOR}.{_MINOR}.{_REVISION}"

1. 给VERSION字典添加明确的类型标注 #

把VERSION: Dict = {}修改为VERSION: Dict[str, str] = {}，明确指定字典的键和值都是字符串类型。类型检查工具会据此推断VERSION["VERSION"]是str类型。

修改后的代码片段：

from typing import Dict
# ...
VERSION: Dict[str, str] = {}

2. 对返回值进行类型断言 #

使用cast函数直接告诉类型检查工具返回值的类型，需要先导入cast：

修改后的返回语句：

from typing import cast
# ...
return cast(str, VERSION["VERSION"])

3. 替换exec方式（更推荐） #

exec本身不利于类型推断，最好把version.py作为模块直接导入，这样类型检查工具能直接识别VERSION的类型：

首先确保package_folder是可导入的模块，然后修改函数：

def write_ini() -> str:
    """Write version.ini file by extracting version from version.py."""
    from package_folder.version import VERSION
    
    print(VERSION)
    config["VERSION"] = {"cv_version": f"v{VERSION}"}

    with open("version.ini", "w") as configfile:
        config.write(configfile)

    return VERSION

这种方式完全避免了exec带来的类型模糊问题，同时代码更简洁安全。

内容的提问来源于stack exchange，提问作者Dawny33