dpkg-query not found on all Linux systems

[matthewhague]

• bleak version: 0.2.2
• Python version: 3.7.1
• Operating System: Arch Linux

Description

The __init__ function fails with "no such file or directory 'dpkg-query'" when using the module. Dpkg is not used on Arch Linux, so i would not expect this check to pass.

What I Did

Started the Python interpreter and attempted
import bleak

Many thanks for the nice looking library!

[hbldh]

Ah, of course. This was an oversight on my part; thank you for bringing it to my attention!

How would you propose to do this on Arch Linux? To use a call to pacman?
Or try to use bluetoothctl --version directly and try to parse that directly since the package is probably already installed? I do not remember why I chose not to do this in the first place, but I think I had a reason.

[hbldh]

Made new release (0.2.3) to PyPI that I think will fix the issue, given that you actually have BlueZ installed on your Arch Linux.

[matthewhague]

Cool, thanks! -- i'd already cheated a bit by commenting out the check. Otherwise it does exactly what i needed, with way less code that the other library i tried.

I had a look around to for a way to check the version in Python, but didn't find anything. With ctype.util.find_library("bluetooth") you can find the bluetooth library version, but i'm not sure that's what you want. If you're using bluez via dbus, i'd hope there is a way of querying the availability and version of services, but don't know enough about dbus to make progress in the time i have.

Using bluetoothctl is probably a reasonable solution. I'd add some kind of catch for when it's not available. Perhaps falling back on dpkg-query. If neither of those work, perhaps just a warning will do?

[matthewhague]

Looking at the names of the Bluez things you use, it looks like Bluez versions its interfaces. Perhaps you don't need to test for a specific Bluez version, and can just try opening the interfaces and taking a failure to mean it's not installed. If the interfaces open, then they should have a compatible interface.

[hbldh]

I will use bluetoothctl --version for the time being, and try to do the checking via DBUS in the future.
Version 0.2.3 was incorrect, but it is solved in 0.2.4.