Transition to pydicom 1.x

Important information on differences in pydicom post 1.0 vs pre-1.0


As is often the case for major software version number changes, pydicom 1.0 breaks with the previous release of pydicom (0.9.9) in several ways. These require changes to user code to target the pydicom >= 1.0 package, or to check and deal with the differences between the versions.

Backwards-compatible changes post 1.0
  • the library is no longer dicom but is pydicom, to match the package name
  • short-form names such as Beams are no longer allowed; use the full keyword e.g. BeamSequence
  • some less-used modules within pydicom have been renamed, e.g. dicom.UID is now pydicom.uid

Why was the package name changed? Yes, this will cause some confusion for a while, and I apologize for this, but it will fade over time. There are several reasons for this change:

  • it is standard python practice for the package and the installed library to have the same name
  • first time users expect to be able to type import pydicom rather than import dicom, which has caused confusion
  • it makes sense for search engines - with the correct name it is much easier to find relevant questions and example code online

The decision wasn’t taken lightly, but with a great deal of discussion on the github issues list. Having made the leap, the rest of this guide should help smooth the way...

For authors of packages requiring pydicom < 1.0

If you have authored code targeting the “old” dicom library, you have three options (at least):

# update the code base to target pydicom >1.0 # update your dependencies to point to package dicom rather than pydicom # update dependencies to explictly target pydicom < 1, e.g. pydicom=0.9.9

The first option can be relatively simple for most projects. If you only use basic pydicom features, e.g. to read and write files, simply changing import dicom to import pydicom everywhere may be all that is needed.

The second and third options will get the same library installed. The second is preferred, as this will point to a repository explicit to the old dicom code. This makes it clear that your code has not been updated for pydicom 1, and allows people to install pydicom and dicom completely independently.

Error messages relating to the pydicom transition

This section is here in the hopes of people getting redirected to this page on searches. If that’s you, then welcome! Hopefully the information here can get things going quickly for you.

For those with pydicom < 1.0 installed, on trying to import pydicom, they will get an ImportError message:

>>> import pydicom
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named pydicom

Your choice then is to update to pydicom >=1.0 (see Installing pydicom section), or to instead use import dicom and follow old-style pydicom syntax.

Conversely, if pydicom >= 1.0 is installed, the error message for import dicom will look like:

>>> import dicom
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named dicom

In this case you likely have installed pydicom >= 1.0, and so dicom library does not exist. You can simply import pydicom instead, and continue with the new pydicom, or, if you really need the old pydicom, then you should:

pip install dicom

and you should be good to go.