sqlalchemy 使用连接
示例
您可以使用上下文管理器打开连接（即从池中请求一个连接）：
with engine.connect() as conn:
result = conn.execute('SELECT price FROM products')
for row in result:
print('Price:', row['price'])有无，但必须手动将其关闭：
conn = engine.connect()
result = conn.execute('SELECT price FROM products')
for row in result:
print('Price:', row['price'])
conn.close()