Question

The following code raises a syntax error:

>>> for i in range(10):
...     print i
...     try:
...        pass
...     finally:
...        continue
...     print i
...
  File "<stdin>", line 6
SyntaxError: 'continue' not supported inside 'finally' clause

Why isn’t a continue statement allowed inside a finally clause?

P.S. This other code on the other hand has no issues:

>>> for i in range(10):
...     print i
...     try:
...        pass
...     finally:
...        break
...
0

If it matters, I’m using Python 2.6.6.

Answer 1

The use of continue in a finally-clause is forbidden because its interpretation would have been problematic. What would you do if the finally-clause were being executed because of an exception?

for i in range(10):
    print i
    try:
       raise RuntimeError
    finally:
       continue        # if the loop continues, what would happen to the exception?
    print i

It is possible for us to make a decision about what this code should do, perhaps swallowing the exception; but good language design suggests otherwise. If the code confuses readers or if there is a clearer way to express the intended logic (perhaps with try: ... except Exception: pass; continue), then there is some advantage to leaving this as a SyntaxError.

Interestingly, you can put a return inside a finally-clause and it will swallow all exceptions including KeyboardInterrupt, SystemExit, and MemoryError. That probably isn’t a good idea either 😉