A decorator to trace pydicom.dataset.Dataset's walk()

trace_sequences.py

from pydicom import DataElement, Dataset


def trace_sequences(walk_callback):
    stacks = {}
    contexts = []

    def add_items(parent: Dataset, elem: DataElement) -> None:
        for item in range(elem.VM):
            contexts.append((parent, elem, item))

    def add_dataset(ds: Dataset) -> None:
        if stacks:
            if id(ds) not in stacks:
                context = contexts.pop(0)
                parent_stack = stacks[id(context[0])]
                if parent_stack:
                    stack = (*parent_stack, context)
                else:
                    stack = (context,)
                stacks[id(ds)] = stack
        else:
            stacks[id(ds)] = None

    def trace_walk(ds: Dataset, elem: DataElement):
        add_dataset(ds)
        if elem.VR == 'SQ':
            add_items(ds, elem)
        trace = stacks[id(ds)]
        walk_callback(ds, elem, trace)

    return trace_walk

Example use:

import pydicom

@trace_sequences
def callback(ds, elem, trace):
    if trace:
        prefix = '.'.join([f"{i[1].keyword}[{i[2]}]" for i in trace]) + '.'
    else:
        prefix = ''
    print(prefix + str(elem.keyword))
    
dcm = pydicom.dcmread('dicom.dcm')
dcm.walk(callback)