Exception raised when accessing private values

[GoogleCodeExporter]

What steps will reproduce the problem?
1. load a dicom fle from a GE MR750 scanner
2. Access any private field. E.g:
   ds[0x0019,0x10e0].value
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)

<ipython console> in <module>()

/usr/lib/python2.6/site-packages/dicom/dataset.pyc in __getitem__(self, key)
    253                 data_elem = read_deferred_data_element(self.filename, self.timestamp, data_elem)
    254             # Hasn't been converted from raw form read from file yet, so do so now:

--> 255             self[tag] = DataElement_from_raw(data_elem)
    256         return dict.__getitem__(self, tag)
    257 

/usr/lib/python2.6/site-packages/dicom/dataset.pyc in __setitem__(self, key, 
value)
    485             private_creator_tag = Tag(tag.group, private_block)
    486             if private_creator_tag in self:
--> 487                 data_element.private_creator = 
self[private_creator_tag].value
    488         dict.__setitem__(self, tag, data_element)

[SNIP REPEATING ERRORS]

/usr/lib/python2.6/site-packages/dicom/dataset.pyc in __getitem__(self, key)
    253                 data_elem = read_deferred_data_element(self.filename, self.timestamp, data_elem)
    254             # Hasn't been converted from raw form read from file yet, so do so now:

--> 255             self[tag] = DataElement_from_raw(data_elem)
    256         return dict.__getitem__(self, tag)
    257 

/usr/lib/python2.6/site-packages/dicom/dataset.pyc in __setitem__(self, key, 
value)
    484             private_block = tag.elem >> 8
    485             private_creator_tag = Tag(tag.group, private_block)
--> 486             if private_creator_tag in self:
    487                 data_element.private_creator = self[private_creator_tag].value
    488         dict.__setitem__(self, tag, data_element)

/usr/lib/python2.6/site-packages/dicom/dataset.pyc in __contains__(self, name)
    118                 return False
    119         if tag:
--> 120             return dict.__contains__(self, tag)
    121         else:
    122             return dict.__contains__(self, name) # will no doubt raise an exception

RuntimeError: maximum recursion depth exceeded

3. Named fields work fine:
   ds[0x0010,0x0010].value
4. Matlab's dicom parser works fine on these files.
5. Loading the files into Matlab and then saving them back out solves the 
problem. (As does any anonymizing that I've tried.)

What is the expected output? What do you see instead?
Accessing any private fields raises exceptions.

What version of the product are you using?
0.9.4-1

Note that I can't attach the problematic files because they contain identifying 
information and anonymizing the files fixes the problem. 

Original issue reported on code.google.com by bob94...@gmail.com on 27 Aug 2010 at 7:04

[GoogleCodeExporter]

I'm not sure where to go with this ... hard to figure out without some more 
information. Since it goes away when rewritten (by matlab or by anonymizing) 
there must be something different about the way the file is originally stored. 

Could you perhaps use pydicom's hex dump or turn on pydicom's debug mode, both 
explained on the Troubleshooting wiki page [1], and then capture part of the 
text around the start of the private data section, and "anonymize" by simply 
replacing values -- both hex bytes and text -- that include confidential 
information, with 00's (bytes) or "-" (text). That would show the structure of 
how the information is stored without exposing any confidential info. And I 
might be able to create from that a file which could reproduce the failure. If 
you want you could send directly to me (my full name, no punctuation, at 
gmail.com).

Thanks
Darcy 

[1] http://code.google.com/p/pydicom/wiki/Troubleshooting

Original comment by darcymason@gmail.com on 1 Sep 2010 at 12:41

• Changed state: Accepted

[GoogleCodeExporter]

I debugged this issue and found that the calls keep going back and forth 
between __getitem__ and __setitem__ for setting the private creator code. The 
code goes into infinite recursion once the private_block becomes 0 (line 484 
above)

For the tag (0x09,0x10e0) for e.g. code goes to set (0x09,0x10) and in the next 
loop goes to (0x09,0x00) and then keeps looping with this tag.

A simple return after a check if private_block == 0 seems to fix this issue. 
May be there is a better fix.

I tried modifying existing test files to reproduce the problem but have not 
succeeded. I think any data set with private attributes (including creator code 
and group lengths for the private group) should help to reproduce the issue.

Original comment by med.diag...@gmail.com on 7 Sep 2010 at 12:21

[GoogleCodeExporter]

After revisiting this I'm thinking it is likely the same problem that was fixed 
in revision f54d9aa6b3. When I first checked it I somehow convinced myself it 
wasn't, but looking again the fix for the if statement in dataset.py --  "and 
tag != private_creator_tag:" does not appear in the error trace (at line 486) 
copied above.

Would you be able to update to that revision (or later) and check if that 
solves your problem? Alternatively, you could just add the the extra 
conditional just quoted and see if that works.

Original comment by darcymason@gmail.com on 9 Sep 2010 at 1:08

[GoogleCodeExporter]

Closing issue as resolved. As in previous comment, I believe the issue was 
resolved in revision f54d9aa6b3.

Original comment by darcymason@gmail.com on 18 Dec 2011 at 4:42

• Changed state: Verified