[wdroz]

In the improved error message [0] how are they able to tell nested attributes without having a big impact in performance? Or maybe this has a big impact on performance, then using exceptions for control flow is deprecated?

    ...
    print(container.area)

> AttributeError: 'Container' object has no attribute 'area'. Did you mean: 'inner.area'?

[0] -- https://docs.python.org/3.15/whatsnew/3.15.html#improved-err...

[edflsafoiewq]

Here's the relevant diff: https://github.com/python/cpython/pull/137968/files#diff-966...

Search is limited to 20 attributes and non-descriptors only to avoid arbitrary code execution.

I assume constructing AttributeErrors isn't highly performance sensitive.

[dotancohen]

  > using exceptions for control flow is deprecated?

Exceptions are for the exceptional cases - the ones that mean normal operations are being suspended and error messages are being generated. Don't use them for control flow.

[mort96]

In Python, an iterator raises a StopIteration exception to indicate to the for loop that the iterator is done iterating.

In Python, the VM raises a KeyboardInterrupt exception when the user hits ctrl+c in order to unwind the stack, run cleanup code and eventually exit the program.

Python is a quite heavy user of exceptions for control flow.

[Hendrikto]

Typically yes, but not in Python. In Python it is quite common and accepted, and sometimes even recommended as Pythonic to use exceptions for control flow. See iterators, for example.

I really dislike this too, but that’s how it is.

[IshKebab]

Using exceptions for flow control has always been a bad idea, despite what they might have said. Perhaps they are generating that message lazily though?

On the other hand it's not like Python really cares about performance....

[formerly_proven]

All iterators in Python use exceptions for flow control, as do all context managers for the abort/rollback case, and it is generally considered Pythonic to use single-indexing (EAFP) instead of check-then-get (LBYL) - generally with indexing and KeyError though and less commonly with attribute access and AttributeError.

[heavy green check mark]

    try:
        data = collection['key']
    except KeyError:
        data = ..try something else..

[red x]

    if 'key' in collection:
         data = collection['key']
    else:
         data = ..try something else..

The latter form also has the genuine disadvantage that nothing ensures the two keys are the same. I've seen typos there somewhat often in code reviews.

[amluto]

I would like to introduce you to StopIteration.