Twain模块引发异常: twain.excTWCC_SEQERROR

Question

我在python中使用twain module开发了一个软件。本软件基于PyQt4。我已经连接到扫描仪，并使用以下代码扫描大量文件：

import twain

sm = twain.SourceManager(0)
ss = sm.OpenSource()
ss.RequestAcquire(0,0)

while True:
    rv = ss.XferImageNatively()
    if rv is None:
        break
    else:
        (handle, count) = rv
        twain.DIBToBMFile(handle, '{}.bmp'.format(uuid.uuid4()))  

扫描操作完成后，图像会像.bmp文件一样保存。一切正常，但是抛出一个异常，程序不能执行另一行代码。异常消息为：

C:\Python34\python.exe C:/Users/PB/PycharmProjects/34Deneme/dene.py
Traceback (most recent call last):
  File "C:/Users/PB/PycharmProjects/34Deneme/dene.py", line 13, in <module>
    rv = ss.XferImageNatively()
  File "C:\Python34\lib\site-packages\twain.py", line 1841, in XferImageNatively
    rv, handle = self._get_native_image()
  File "C:\Python34\lib\site-packages\twain.py", line 1787, in _get_native_image
    (TWRC_XFERDONE, TWRC_CANCEL))
  File "C:\Python34\lib\site-packages\twain.py", line 1453, in _call
    return self._sm._call(self._id, dg, dat, msg, buf, expected_returns)
  File "C:\Python34\lib\site-packages\twain.py", line 2094, in _call
    raise exc
twain.excTWCC_SEQERROR
Exception ignored in: <bound method SourceManager.__del__ of <twain.SourceManager object at 0x004EEA10>>
Traceback (most recent call last):
  File "C:\Python34\lib\site-packages\twain.py", line 2059, in __del__
  File "C:\Python34\lib\site-packages\twain.py", line 2066, in close
  File "C:\Python34\lib\_weakrefset.py", line 101, in pop
KeyError: 'pop from empty WeakSet'

Process finished with exit code 1

那么问题出在哪里呢？我该如何解决这个问题呢？

Answer 1

    import twain

sm = twain.SourceManager(0)
ss = sm.OpenSource()
ss.RequestAcquire(0,0)
try:
  while True:
    rv = ss.XferImageNatively()
    if rv is None:
        break
    else:
        (handle, count) = rv
        twain.DIBToBMFile(handle, '{}.bmp'.format(uuid.uuid4()))  
except:
  print "Error!"