We have a suite of selenium tests that on setup and teardown open and close the browser to start a new test.
This approach takes a long time for tests to run as the opening and closing is slow. Is there any way to open the browser once in the constructor then reste on setup and cleanup on teardown, then on the deconstructor close the browser?
Any example would be really appreciated.
You can use class or module level setup and teardown methods instead of test level setup and teardown.  Be careful with this though, as if you don't reset your test environment explicitly in each test, you have to handle cleaning everything out (cookies, history, etc) manually, and recovering the browser if it has crashed, before each test.
Selenium test suite only open browser once