Determining if file is valid image file

[André]

On Aug 2, 11:14 am, André <andre.robe... at gmail.com> wrote:
> Other than installing PIL, is there a "simple" way using Python only
> to determine if a file is a valid image file?
>
> I'd be happy if I could at least identify valid images files for gif,
> jpeg and png.   Pointers to existing modules or examples would be
> appreciated.
>
> The reason why I'd prefer not using PIL is that I'd like to bundle
> such a function/module in my app.
>
> André

I should have added: I'm interesting in validating the file *content*
- not the filename :-)