Sarah Weddington, a senior assistant to President Carter, said yesterday that she expects her boss to fill the next vacancy on the Supreme Court with a woman.

"I had lunch with him two weeks ago, and he said he'd love to be the president to put the first woman on the Supreme Court," Weddington told about 100 people attending the Virginia Young Democrats convention at the Springfield Hilton.

While stressing that President Carter had made no firm commitment to name a woman to the high court, Weddington said she expected supporters of the idea to come up with good candidates for the job.

"I have my list, Rosalynn has her list, Attorney General [Griffin] Bell has his and the president has his list," Weddington said.

"We have asked [Virgina Sen.] Harry Byrd for his list," she joked, referring to the state's senior senator's recent nomination of 10 white maies for federal judgeships.

In addition to Weddington's appearance, representatives of the state's 1,260 Young Democrats members heard District of Columbia Mayor Marion Barry urge their support of the District's voting rights amendment when it again comes before the Virginia General Assembly.

Barry and State Sen. Joseph V. Gartlan Jr. (D-Fairfax) were the convention's luncheon speakers. Gartlan discussed the legislature's failure to pass a bill he sponsored that would have revamped the state's sexual assault laws.

The convention had earlier adopted resolutions supporting the D.C. votings rights amendment and the sexual assault bill.