Before entering upon the duties of his office, each officer of the City, whether elected or appointed under the provisions of this Charter, or under any ordinance of the City, shall take and subscribe an oath of office, in the form of the official oath required by the constitution. The oath so taken and subscribed, if by an official required to give a bond, shall be endorsed upon or attached to the bond; if by an official not required to give a bond, such oaths shall be filed with and kept by the City Clerk.