What does "finally: pass" do in Python? (e.g. in try – except – finally)

Question

I would have assumed a finally clause with only a pass to be pointless.

But in a Bottle template, the following code for an optional include would not work without it.
The result would contain everything before, and the included code itself, but nothing after it.
(See the corresponding question.)

try:
    include(optional_view)
except NameError:
    pass
finally:
    pass

What does finally: pass do, and when is it useful?

Answer 1

finally: pass does nothing, but you don't actually have finally: pass. You're writing a Bottle template, not Python, and you have broken Bottle template syntax.

Bottle templates ignore indentation in inline code, which means they need a different way to tell when a block statement ends. Bottle templates use a special end keyword for this. Your try-except needs an end:

try:
    whatever()
except NameError:
    pass
end

Otherwise, the except block continues, and stuff that wasn't supposed to go in the except is considered part of the except.

With finally: pass, the stuff that was incorrectly part of the except is now incorrectly part of the finally, so it runs in cases where it wouldn't have run as part of the except.

Answer 2

The ‘finally’ keyword in Python is used to ensure that code within the “finally” block will always be executed, regardless of whether an exception occurs or not, where if an exception does occur within the “try” block, both the appropriate “except” and then finally blocks would execute; however, if no exceptions occurred only the finally block would run after completion of try. So in that case, the except clause makes a difference, even though the pass statement itself is still just a placeholder.