Meredith Weenick, Boston’s chief financial officer, announced Thursday that she will leave city government in April after helping Mayor Martin J. Walsh submit his first budget. Weenick worked for the administration of former mayor Thomas M. Menino for 11 years. She become the city’s chief financial officer in 2010 after the departure of Lisa Calise Signori. “I’m excited to move on to explore other opportunities,’’ Weenick said in an e-mail. “Mayor Walsh and I discussed my decision back in December. My focus remains on managing the City’s finances and presenting a responsible, balanced budget that serves the residents of Boston.’’ Weenick started with the city in 2002 as the first in what became a long line of fellows from Harvard Business School. Lisa Pollack, a spokeswoman for the Walsh administration, said that Weenick has helped put Boston in its tiptop financial shape. “We can’t underestimate the role Meredith has played in getting us there,’’ Pollack said.