how to read only metadata from a dicom url

dicom_over_http.py

"""
how to read only metadata from a dicom url to save bandwith

- note the server must support HTTP Range, e.g. s3 buckets or azure blobs.
- note that if you don't mind reading the whole thing, it's easier to just read the whole thing, then pass it into pydicom as io.BytesIO


url: https://gist.github.com/wassname/70106b2d66a7c6e83e4b0300c9d1d4d3
"""

import httpio
import pydicom

class HTTPIOFile2(httpio.HTTPIOFile):
    """
    We want the open url to act like an open file for pidicom

    httpio helps, but does not return an EOFError which pydicom waits for...
    """
    def seek(self, *args, **kwargs):
        try:
            super().seek(*args, **kwargs)
        except httpio.HTTPIOError as e:
            if 'Invalid argument: cursor=' in e.args[0]:
                raise EOFError
            else:
                raise


def dcmread_http(url, stop_before_pixels=True, force=True):
    """
    
    """
    with HTTPIOFile2(url, block_size=1024) as r:
        dcm = pydicom.dcmread(r, stop_before_pixels=stop_before_pixels, defer_size="2 KB", force=force)
    return dcm

# test
url = ""
dcm = dcmread_http(url)
assert dcm is not None
print(dcm)