ImportError: failed to locate hidapi shared object on macOS Catalina about blynclight HOT 4 CLOSED

Since reporting the issue, I was able to get this to work:

1. Tried to compile hidapi directly on macOS Catalina, which I couldn't get to work.
2. Compiled hidapi on macOS Mojave, which installed it to /usr/local/lib.
3. I was able to use hidapi and this module on Mojave to control a Blynclight. Yay!
4. Copied that and installed the hidapi files to the same location on macOS Catalina.
5. I was able to use this module on Catalina to control a Blynclight.
6. Profit!

So, it seems like the problem is either with a) what the MacPorts port command produced or b) with the location where it was installed. MacPorts installs under /opt.

Assuming it compiled correctly, I'm wondering if the /opt location is or can be searched for the library. I'm not sure how to check — or set — that for libraries (like PATH for executables).

From MacPorts:

$ ls -1 /opt/local/lib/ | grep hid
libhidapi.0.dylib
libhidapi.a
libhidapi.dylib

What I copied from macOS Mojave:

$ ls -1 /usr/local/lib/ | grep hid
libhidapi.0.dylib
libhidapi.a
libhidapi.dylib
libhidapi.la

Update: I found these references:

• ctypes — A foreign function library for Python
• Which paths does python ctypes module search for libraries on Mac OS?
  

The MacPorts path of /opt is not in the list, per the Stackoverflow article. I'm still not sure how to / if it's possible to add a path for ctypes.util.find_library to search.

Update 2: Also found something that appears similar:

• Importing sdl2 in python3.3 gives PYSDL2_DLL_PATH: unset

I will keep looking to find a way to add /opt.

from blynclight.

The error in your traceback comes from ctypes.util.find_library failing to find the installed hidapi library.

import ctypes.util

print(ctypes.util.find_library('hidapi'))

I'm not familiar with port so I don't know how it manages the files it installs.

from blynclight.

Thanks for all the detailed information on what you had to do to get BlyncLight running!

I'll dig into find_library and see if I can improve how the shared library is located.

from blynclight.

So looking at the code for ctypes.util.macholib.dylib I found an environment variable you can set to help find_library .. uh.. find the library.

$ export DYLD_FALLBACK_LIBRARY_PATH=/opt/local/lib

I tested this on my macOS 10.15.5 installation after installing Mac Ports:

$ which port
/opt/local/bin/port
$ brew uninstall hidapi
...
$ blync -a
<blows up>
$ sudo port install hidapi
...
$ blync -a
<still blows up, expected>
$ export DYLD_FALLBACK_LIBRARY_PATH=/opt/local/lib
$ blync -a
Number of available lights: 1
                 KEY:ID:VALUE
                path:00:IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/TRP0@7/IOPP/PXSX@0/IOPP/pci-bridge@2/IOPP/pci1b21,1242@0/AppleUSBXHCIPCI@00000000/AppleUSB20XHCIPort@00300000/Blynclight Plus@00300000/IOUSBHostInterface@0/AppleUserUSBHostHIDDevice
           vendor_id:00:0x2c0d
          product_id:00:0x10
      release_number:00:0x100
      product_string:00:Blynclight Plus
          usage_page:00:0xff00
               usage:00:0x1
    interface_number:00:0x0

Add that to your shell's profile script and you should be able to skip copying things to /usr/local.

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