如何在SQLAlchemy中动态使用select？

from sqlalchemy import create_engine, select, MetaData, Table, Column, Integer, String
from sqlalchemy.orm import sessionmaker

engine = create_engine('数据库连接字符串')
Session = sessionmaker(bind=engine)
session = Session()

metadata = MetaData()
my_table = Table('my_table', metadata,
                 Column('id', Integer, primary_key=True),
                 Column('name', String),
                 Column('age', Integer),
                 Column('gender', String)
                 )

columns = [my_table.c.name, my_table.c.age]  # 根据需要选择的列
query = select(columns)

# 添加条件
if condition1:
    query = query.where(my_table.c.age > 18)
if condition2:
    query = query.where(my_table.c.gender == 'male')

# 执行查询
result = session.execute(query).fetchall()