def select_by_ext(self, ext, recursive=True):
        """
        Select file path by extension.

        :param ext:

        **中文文档**

        选择与预定义的若干个扩展名匹配的文件。
        """
        ext = [ext.strip().lower() for ext in ensure_list(ext)]

        def filters(p): return p.suffix.lower() in ext

        return self.select_file(filters, recursive)