Error when importing libusb1 on Windows

[bauerj]

Using 0.9.0 on Windows yields this error:

 bauerj@DESKTOP-5KP26RC  ~  python
Python 3.6.2 (v3.6.2:5fd33b5, Jul  8 2017, 04:14:34) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from trezorlib.device import TrezorDevice
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "c:\python3.6.2\lib\site-packages\trezorlib\device.py", line 23, in <module>
    from .transport_webusb import WebUsbTransport
  File "c:\python3.6.2\lib\site-packages\trezorlib\transport_webusb.py", line 24, in <module>
    import usb1
  File "c:\python3.6.2\lib\site-packages\usb1\__init__.py", line 61, in <module>
    from . import libusb1
  File "c:\python3.6.2\lib\site-packages\usb1\libusb1.py", line 199, in <module>
    libusb = _loadLibrary()
  File "c:\python3.6.2\lib\site-packages\usb1\libusb1.py", line 173, in _loadLibrary
    return dll_loader('libusb-1.0' + suffix, **loader_kw)
  File "c:\python3.6.2\lib\ctypes\__init__.py", line 348, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: [WinError 126] The specified module could not be found

[prusnak]

That is a result of non-working installation of python-libusb1 dependency. Please see the following issue for resolution: vpelletier/python-libusb1#7

[bauerj]

Does it mean that pip installs a broken version of python-libusb1 by default or that this is merely an issue with my installation?

[prusnak]

I guess that python-libusb1 does not install the required libusb-1.0 dll by default, but best would be to ask in the linked issue.

[bauerj]

I think that is correct. In that case, wouldn't it make sense to add that to the installation instructions for python-trezor?

[prusnak]

I agree, but let's first find out what to put there ...

[bauerj]

For me, the following worked:

1. Download libusb-1.0.21.7z
2. Copy MS{32,64}\dll\libusb-1.0.dll to the location of your python.exe