libusb似乎在类编码结构下失败了，但在没有类编码结构的情况下可以工作吗？
libusb似乎在类编码结构下失败了，但在没有类编码结构的情况下可以工作吗？
提问于 2011-09-12 13:05:45
我有一个使用Python/ NXT /libusb的简单工作示例，如下所示(注意:使用具有USB接口的乐高NXT)：
import nxt.locator
from nxt.motor import *
def flip_cube(b):
m_arm = Motor(b, PORT_B)
m_arm.turn(75, 85)
m_arm.turn(-50, 85)
b = nxt.locator.find_one_brick()
flip_cube(b)上面的工作正常。
作为训练练习，我尝试将python代码“对象化”，这样我就可以开始在代码周围放置库，但是现在LibUSB库抱怨说它找不到usb设备。哈?我做错了什么。下面是我尝试使用类结构编写的代码：
import nxt.locator
from nxt.motor import *
class BasicRobotTestCase():
__test__ = True
def __init__(self):
b = nxt.locator.find_one_brick()
def flip_cube(self):
m_arm = Motor(b, PORT_B)
m_arm.turn(75, 85)
m_arm.turn(-50, 85)
def test_flip_cube(self):
flip_cube()当我执行上面的代码时，我得到了以下错误(即使我重新执行第一个示例，它仍然执行得很好)：
E
======================================================================
ERROR: Failure: USBError (No such device (it may have been disconnected))
----------------------------------------------------------------------
Traceback (most recent call last):
File "/Library/Python/2.6/site-packages/nose-0.11.4-py2.6.egg/nose/loader.py", line 485, in makeTest
return self._makeTest(obj, parent)
File "/Library/Python/2.6/site-packages/nose-0.11.4-py2.6.egg/nose/loader.py", line 539, in _makeTest
return MethodTestCase(obj)
File "/Library/Python/2.6/site-packages/nose-0.11.4-py2.6.egg/nose/case.py", line 331, in __init__
self.inst = self.cls()
File "/Users/gnunez/git-projects/pdca_automation/rubics/tests/basic_robot_test_case.py", line 8, in __init__
b = nxt.locator.find_one_brick()
File "/Users/gnunez/git-projects/pdca_automation/nxt/locator.py", line 112, in find_one_brick
for s in find_bricks(host, name, silent, method):
File "/Users/gnunez/git-projects/pdca_automation/nxt/locator.py", line 43, in find_bricks
for s in socks:
File "/Users/gnunez/git-projects/pdca_automation/nxt/usbsock.py", line 83, in find_bricks
for bus in usb.busses():
File "build/bdist.macosx-10.6-universal/egg/usb/legacy.py", line 330, in busses
return (Bus(),)
File "build/bdist.macosx-10.6-universal/egg/usb/legacy.py", line 326, in __init__
self.devices = [Device(d) for d in core.find(find_all=True)]
File "build/bdist.macosx-10.6-universal/egg/usb/legacy.py", line 311, in __init__
self.configurations = [Configuration(c) for c in dev]
File "build/bdist.macosx-10.6-universal/egg/usb/core.py", line 706, in __iter__
yield Configuration(self, i)
File "build/bdist.macosx-10.6-universal/egg/usb/core.py", line 407, in __init__
configuration
File "build/bdist.macosx-10.6-universal/egg/usb/_debug.py", line 52, in do_trace
return f(*args, **named_args)
File "build/bdist.macosx-10.6-universal/egg/usb/backend/libusb10.py", line 423, in get_configuration_descriptor
config, byref(cfg)))
File "build/bdist.macosx-10.6-universal/egg/usb/backend/libusb10.py", line 357, in _check
raise USBError(_str_error[retval.value])
USBError: No such device (it may have been disconnected)回答 1
Stack Overflow用户
发布于 2011-09-12 15:51:51
创建BasicRobotTestCase时，如果不将其存储为实例(即self.b)的成员，则会丢失b变量
编辑：好吧，self的缺失并不是问题的根源，也许是鼻子实例化你的类的方式变成了U盘抓取，试着直接实例化这个类。
import nxt.locator
from nxt.motor import *
class BasicRobotTestCase():
__test__ = True
def __init__(self):
self.b = nxt.locator.find_one_brick() # Store the brick in self.b
def flip_cube(self):
m_arm = Motor(self.b, PORT_B) # use the stored brick in self.b to create the motor
m_arm.turn(75, 85)
m_arm.turn(-50, 85)
def test_flip_cube(self):
self.flip_cube()
if __name__=="__main__":
BasicRobotTestCase().test_flip_cube()页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/7383508
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