pydicom.dataelem.DataElement¶

class pydicom.dataelem.DataElement(tag: int | str | tuple[int, int], VR: str, value: Any, file_value_tell: int | None = None, is_undefined_length: bool = False, already_converted: bool = False, validation_mode: int | None = None)[source]¶

Contain and manipulate a DICOM Element.

Examples

While its possible to create a new DataElement directly and add it to a Dataset:

>>> from pydicom import Dataset
>>> elem = DataElement(0x00100010, 'PN', 'CITIZEN^Joan')
>>> ds = Dataset()
>>> ds.add(elem)

Its far more convenient to use a Dataset to add a new DataElement, as the VR and tag are determined automatically from the DICOM dictionary:

>>> ds = Dataset()
>>> ds.PatientName = 'CITIZEN^Joan'

Empty DataElement objects (e.g. with VM = 0) show an empty string as value for text VRs and None for non-text (binary) VRs:

>>> ds = Dataset()
>>> ds.PatientName = None
>>> ds.PatientName
''

>>> ds.BitsAllocated = None
>>> ds.BitsAllocated

>>> str(ds.BitsAllocated)
'None'

descripWidth¶

For string display, this is the maximum width of the description field (default 35).

Type:: int

is_undefined_length¶

Indicates whether the length field for the element was 0xFFFFFFFFL (ie undefined).

Type:: bool

maxBytesToDisplay¶

For string display, elements with values containing data which is longer than this value will display "array of # bytes" (default 16).

Type:: int

showVR¶

For string display, include the element’s VR just before it’s value (default True).

Type:: bool

tag¶

The element’s tag.

Type:: pydicom.tag.BaseTag

validation_mode¶

The mode used to validate the element’s value. See Settings.writing_validation_mode for more information.

Type:: int

VR¶

The element’s Value Representation.

Type:: str

__init__(tag: int | str | tuple[int, int], VR: str, value: Any, file_value_tell: int | None = None, is_undefined_length: bool = False, already_converted: bool = False, validation_mode: int | None = None) → None[source]¶

Create a new DataElement.

Parameters:

tag (int | str | tuple[int, int]) – The DICOM (group, element) tag in any form accepted by Tag() such as 'PatientName', (0x10, 0x10), 0x00100010, etc.
VR (str) – The 2 character DICOM value representation (see DICOM Standard, Part 5, Section 6.2).
value (Any) –
The value of the data element, the allowed type depends on the VR and includes:
- a single str value
- an int or int
- a list or tuple containing only a single type of item such as str, int or float
- a raw bytes value
file_value_tell (int, optional) – The byte offset to the start of the encoded element value.
is_undefined_length (bool, optional) – Used internally to store whether the length field for this element was 0xFFFFFFFF, i.e. ‘undefined length’. Default is False.
already_converted (bool, optional) – Used to determine whether or not the element’s value requires conversion to a value with VM > 1. Default is False.
validation_mode (int, optional) – Defines if values are validated and how validation errors are handled.

Methods

`__init__`(tag, VR, value[, file_value_tell, ...])	Create a new `DataElement`.
`clear`()	Clears the value, e.g. sets it to the configured empty value.
`from_json`(dataset_class, tag, vr, value, ...)	Return a `DataElement` from a DICOM JSON Model attribute object.
`to_json`([bulk_data_threshold, ...])	Return a JSON representation of the `DataElement`.
`to_json_dict`(bulk_data_element_handler, ...)	Return a dictionary representation of the `DataElement` conforming to the DICOM JSON Model as described in the DICOM Standard, Part 18, Annex F.
`validate`(value)	Validate the current value against the DICOM standard.

Attributes

`VM`	Return the value multiplicity of the element as `int`.
`descripWidth`
`empty_value`	Return the value for an empty element.
`is_buffered`	Return `True` if the element's value is a `io.BufferedIOBase` instance, `False` otherwise.
`is_empty`	Return `True` if the element has no value.
`is_private`	Return `True` if the element's tag is private.
`is_raw`
`is_retired`	Return the element's retired status as `bool`.
`keyword`	Return the element's keyword (if known) as `str`.
`maxBytesToDisplay`
`name`	Return the DICOM dictionary name for the element as `str`.
`repval`	Return a `str` representation of the element's value.
`showVR`
`value`	Get or set the element's value.

property VM: int¶: Return the value multiplicity of the element as int.

Changed in version 3.0: SQ elements now always return a VM of 1.

clear() → None[source]¶

Clears the value, e.g. sets it to the configured empty value.

See empty_value_for_VR().

property empty_value: bytes | list[str] | None | str | PersonName¶

Return the value for an empty element.

See empty_value_for_VR() for more information.

Returns:: The value this data element is assigned on decoding if it is empty.
Return type:: str or None

Return a DataElement from a DICOM JSON Model attribute object.

Parameters:

dataset_class (dataset.Dataset derived class) – The class object to use for SQ element items.
tag (str) – The data element’s tag as uppercase hex.
vr (str) – The data element’s value representation (VR).
value (str or list[None | str | int | float | bytes | dict]) – The data element’s value(s).
value_key (str or None) – The attribute name for value, should be one of: {"Value", "InlineBinary", "BulkDataURI"}. If the element’s VM is 0 and none of the keys are used then will be None.
bulk_data_uri_handler (callable or None) – Callable function that accepts either the tag, vr and “BulkDataURI” value or just the “BulkDataURI” value of the JSON representation of a data element and returns the actual value of that data element (retrieved via DICOMweb WADO-RS). If no bulk_data_uri_handler is specified (default) then the corresponding element will have an “empty” value such as "", b"" or None depending on the vr (i.e. the Value Multiplicity will be 0).

Return type:

DataElement

property is_buffered: bool¶: Return True if the element’s value is a io.BufferedIOBase instance, False otherwise.

property is_empty: bool¶: Return True if the element has no value.

property is_private: bool¶: Return True if the element’s tag is private.

Added in version 2.1.

property is_retired: bool¶

Return the element’s retired status as bool.

For officially registered DICOM Data Elements this will be True if the retired status as given in the DICOM Standard, Part 6, Table 6-1 is ‘RET’. For private or unknown elements this will always be False.

property keyword: str¶

Return the element’s keyword (if known) as str.

For officially registered DICOM Data Elements this will be the Keyword as given in Table 6-1. For private or unknown elements this will return an empty string ''.

property name: str¶

Return the DICOM dictionary name for the element as str.

Returns:

For officially registered DICOM Data Elements this will be the Name as given in Table 6-1.
For private elements known to pydicom this will be the Name in the format '[name]'.
For unknown private elements this will be 'Private tag data'.
Otherwise returns an empty string ''.

Return type:

str

property repval: str¶: Return a str representation of the element’s value.

to_json(bulk_data_threshold: int = 1024, bulk_data_element_handler: Callable[[DataElement], str] | None = None, dump_handler: Callable[[dict[str, Any]], str] | None = None) → str[source]¶

Return a JSON representation of the DataElement.

Parameters:

bulk_data_threshold (int, optional) – Size of base64 encoded data element above which a value will be provided in form of a “BulkDataURI” rather than “InlineBinary”. Ignored if no bulk_data_element_handler is given.
bulk_data_element_handler (callable, optional) – Callable that accepts a bulk :class`data element <pydicom.dataelem.DataElement>` and returns the “BulkDataURI” as a str for retrieving the value of the data element via DICOMweb WADO-RS.
dump_handler (callable, optional) – Callable function that accepts a dict of {str: Any} and returns the serialized (dumped) JSON str (by default uses json.dumps()).

Returns:

Mapping representing a JSON encoded data element

Return type:

str