The qualified voters of the city and county of Philadelphia, and of each and every county in the state, shall, at the general election on the second Tuesday of October next, and every three years thereafter, elect one person, learned in the law, who has been two year admitted to the bar, and who shall have resided in the county for which he is elected for one year next preceding his election, who shall be called the district attorney of said county.
16 P.S. § 7701