Python 3.4.1 (v3.4.1:c0e311e010fc, May 18 2014, 10:38:22) [MSC v.1600 32 bit (Intel)] on win32
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>>> import sys
>>> sys.path.append('d:pyusb-1.0.0a2usb')
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 16-17: truncated uXXXX escape

>>> sys.path.append(r'd:pyusb-1.0.0a2usb')

>>> sys.path.append('d:\pyusb-1.0.0a2\usb')

>>> sys.path.append('d:/pyusb-1.0.0a2/usb')