[Python-Dev] When to use EOFError? (original) (raw)

Random832 random832 at fastmail.com
Wed Jun 22 10:31:27 EDT 2016

On Tue, Jun 21, 2016, at 16:48, Serhiy Storchaka wrote:

There is a design question. If you read file in some format or with some protocol, and the data is ended unexpectedly, when to use general EOFError exception and when to use format/protocol specific exception?

For example when load truncated pickle data, an unpickler can raise EOFError, UnpicklingError, ValueError or AttributeError. It is possible to avoid ValueError or AttributeError, but what exception should be raised instead, EOFError or UnpicklingError? Maybe convert all EOFError to UnpicklingError?

I think this is the most appropriate. If the calling code needs to know the original reason it can find it in cause.

My instinct, though, (and I'm aware that others may not agree, but I thought it was worth bringing up) is that loads should actually always raise a ValueError, i.e. my mental model of loads is like:

def loads(s): f = BytesIO(s) try: return load(f) except UnpicklingError as e: raise ValueError from e

More information about the Python-Dev mailing list