Cleaning up with try / catch / finally

This lesson covers cleanup with Julia's try / catch / finally, with the aim of running something whether or not an error occurred.

A finally block always runs, exception or no exception. Use it to close a file or to signal that work has finished.

In the sample code, divide() catches a division-by-zero error with catch e and always shows "Ending the calculation" from the finally block, error or not. Note how e.msg pulls the error message out.

A common early stumble is when finally runs. Even if the try block returns, finally runs first — miss that ordering and the flow is easy to misread.

In professional work, finally is used wherever an external resource such as a file or a database connection has been opened and must reliably be closed, however things end.

📖 Reference code

function divide(a, b)
    try
        if b == 0
            error("cannot divide by zero")
        end
        return div(a, b)
    catch e
        println("Error: ", e.msg)
        return nothing
    finally
        println("Ending the calculation")
    end
end

println(divide(10, 2))
divide(10, 0)

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Julia directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).