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If loading libusb1 failed, perhaps due to a missing symbol, a second
call to libusb1.get_backend would reuse partially constructed prototypes
and return an unsound _LibUSB instance.[1]

To fix this, remove the previous optimization and load/setup the library
every time.

[1] #333 (comment)

Related: #333 ("show_devices() segfaults when run twice")

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PyUSB 1.0 - Easy USB access from Python


The PyUSB module provides for Python easy access to the host machine's Universal Serial Bus (USB) system.

Until 0.4 version, PyUSB used to be a thin wrapper over libusb. With the 1.0 version, things changed considerably: now PyUSB is an API rich, backend neutral Python USB module easy to use.

As with most Python modules, PyUSB's documentation is based on Python doc strings and can therefore be manipulated by tools such as pydoc.

You can also find a tutorial at docs/tutorial.rst.

PyUSB is being developed and tested on Linux and Windows, but it should work fine on any platform running Python >= 2.4, ctypes and at least one of the builtin backends.

PyUSB supports libusb 1.0, libusb 0.1 and OpenUSB, but the user does not need to worry about that, unless in some corner cases.

If you have any question about PyUSB, consult the FAQ at docs/faq.rst or the PyUSB mailing list hosted in the SourceForge. In the PyUSB website you can find instructions on how to subscribe to the mailing list.


PyUSB is installed through pip:

pip install pyusb

Remember that you need libusb (1.0 or 0.1) or OpenUSB running on your system. For Windows users, libusb 1.0 DLLs are provided in the releases (see 7z archives). Check the libusb website for updates (

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