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Exception "'NoneType' object has no attribute 'decode'" when character set is empty. #1038

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micjuel opened this issue Jan 21, 2020 · 6 comments · Fixed by #1039
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Exception "'NoneType' object has no attribute 'decode'" when character set is empty. #1038

micjuel opened this issue Jan 21, 2020 · 6 comments · Fixed by #1039
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@micjuel
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micjuel commented Jan 21, 2020

Describe the bug
If Transfer Syntax UID(0002,0010) is "1.2.840.10008.1.2" (LEI) and Character Set(0008,0005) is empty (that is assuming "ISO-IR 6"), there is an exception ("'NoneType' object has no attribute 'decode'").

Expected behavior
No exception. Defaulting to ISO-IR 6.

Steps To Reproduce
Use the attached dcm file and run :

ds = pydicom.dcmread("empty_charset_LEI.dcm")

Traceback:

Exception has occurred: AttributeError
'NoneType' object has no attribute 'decode'
  File "C:\Program Files\Python38\Lib\site-packages\pydicom\values.py", line 370, in convert_string
    byte_string = byte_string.decode(default_encoding)
  File "C:\Program Files\Python38\Lib\site-packages\pydicom\filereader.py", line 208, in data_element_generator
    encoding = convert_string(value, is_little_endian)
  File "C:\Program Files\Python38\Lib\site-packages\pydicom\filereader.py", line 378, in read_dataset
    raw_data_element = next(de_gen)
  File "C:\Program Files\Python38\Lib\site-packages\pydicom\filereader.py", line 751, in read_partial
    dataset = read_dataset(fileobj, is_implicit_VR, is_little_endian,
  File "C:\Program Files\Python38\Lib\site-packages\pydicom\filereader.py", line 878, in dcmread
    dataset = read_partial(fp, stop_when, defer_size=defer_size,
  File "D:\test_dicom.py", line 57, in <module>
    ds = pydicom.dcmread(filename)

Your environment
Windows-10-10.0.18362-SP0
Python 3.8.1 (tags/v3.8.1:1b293b6, Dec 18 2019, 23:11:46) [MSC v.1916 64 bit (AMD64)]
pydicom 1.4.1

empty_charset_LEI.zip
@micjuel micjuel changed the title Got exception "'NoneType' object has no attribute 'decode'" Exception "'NoneType' object has no attribute 'decode'" when character set is empty. Jan 21, 2020
@mrbean-bremen
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This is strictly speaking invalid DICOM (Specific Character Set is type 1C and cannot be empty), and I have never seen that so far. Anyway, it makes sense to handle this case as a missing tag (e.g. ISO-IR 6).

@mrbean-bremen
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And given that empty values can always happen (despite the standard) we should always handle it without crashing, so this a bug anyway IMO.

@micjuel
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micjuel commented Jan 21, 2020

After verification, you are right, it is strictly speaking invalid DICOM.

@mrbean-bremen
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Can we use your example dataset for testing? It is a nice little dataset.

@micjuel
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micjuel commented Jan 21, 2020

Yes for sure.

mrbean-bremen added a commit to mrbean-bremen/pydicom that referenced this issue Jan 21, 2020
@mrbean-bremen
Correctly handle reading empty Specific Character Set
63343fe 
- fixes pydicom#1038
@mrbean-bremen mrbean-bremen mentioned this issue Jan 21, 2020
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darcymason pushed a commit that referenced this issue Jan 21, 2020
@mrbean-bremen @darcymason
Correctly handle reading empty Specific Character Set (#1039)
e9a89e5 
* Correctly handle reading empty Specific Character Set

- fixes #1038

* Removed unneeded check for Specific Character Set

- the check was for a tag with undefined length, which cannot be
  Specific Character Set
@mrbean-bremen mrbean-bremen mentioned this issue Feb 4, 2020
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@mrbean-bremen mrbean-bremen mentioned this issue Feb 19, 2020
Closed
darcymason pushed a commit that referenced this issue Feb 20, 2020
@mrbean-bremen @darcymason
Correctly handle reading empty Specific Character Set (#1039)
b9999a8 
* Correctly handle reading empty Specific Character Set

- fixes #1038

* Removed unneeded check for Specific Character Set

- the check was for a tag with undefined length, which cannot be
  Specific Character Set
@scaramallion
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Should be fixed with v1.4.2

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[MRG] Correctly handle reading empty Specific Character Set mrbean-bremen/pydicom
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@mrbean-bremen @scaramallion @micjuel