[Python-Dev] When to use EOFError?

André Malo nd at perlig.de
Wed Jun 22 12:22:49 EDT 2016

* 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? Or all UnpicklingError caused by unexpectedly ended
> input to EOFError? Or raise EOFError if the input is ended after
> completed opcode, and UnpicklingError if it contains truncated opcode?

I often concatenate multiple pickles into one file. When reading them, it 
works like this:

    while True:
        yield pickle.load(fp)
except EOFError:

In this case the truncation is not really unexpected. Maybe it should 
distinguish between truncated-in-the-middle and truncated-because-empty.

(Same goes for marshal)

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