[sane-devel] python-sane - checking for active device

[m. allan noah]

On Tue, 21 Mar 2006, Horst Herb wrote:

> What is the correct way of checking whether a device is available (plugged in,
> switched on) using the python SANE interface?
>
> If I switch my scanner off, sane.get_devices(), sane keeps reporting the
> scanner as if it was still available.
>
> If I start the program with the scanner switched off, and switch it on *after*
> calling sane.get_devices(), no scanner is found.
>

i am willing to bet that is a mis-designed sane backend. the sane spec 
says that a front end can call sane_get_devices to learn about newly 
attached scanners. but most backends that i have seen are written 
incorrectly, and load the list of scanners into a global in sane_init 
only.

of course, i could be wrong, and the python layer could be doing something 
strange, i know nothing of that.

i would suggest that you read the source for the backend you use, and 
maybe turn up its debug vars when running your py program.

allan

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