Element VRs and Python types¶

DICOM elements can contain anything from ASCII strings to unicode text, decimals, floats, signed and unsigned integers of different byte-depth and even encoded data. The format of the value of an element is given by its Value Representation or VR, and a list of VRs is given in the DICOM Standard in Part 5, Table 6.2-1.

So when using pydicom, what Python type should be used with a given VR to ensure that the value gets written correctly?

Elements of any VR:
- Can be set as empty by using None
- Can have their values set using their set using or stored as type from the table below
Non-SQ element values:
- Can also be set using a list of their set using type - for Value Multiplicity (VM) > 1, the value will be stored as a MultiValue of their stored as type
- However, according to the DICOM Standard, elements with VR LT, OB, OD, OF, OL, OW, ST, UN, UR and UT should never have a VM greater than 1.
SQ element values should be set using a list of zero or more Dataset instances.

VR	Name	Set using	Stored as (T)	Type hint for element value
AE	Application Entity	`str`	`str`	Union[None, T, MutableSequence[T]]
AS	Age String	`str`	`str`
AT	Attribute Tag	Tag ¹	`BaseTag`
CS	Code String	`str`	`str`
DA	Date	`str`	`str` or `DA`²
DS	Decimal String	`str`, `float` or `int`	`DSfloat` or `DSdecimal`³
DT	Date Time	`str`	`str` or `DT`²
FL	Floating Point Single	`float`	`float`
FD	Floating Point Double	`float`	`float`
IS	Integer String	`str` or `int`	`IS`
LO	Long String	`str`	`str`
LT	Long Text	`str`	`str`	Optional[T]
OB	Other Byte	`bytes`	`bytes`
OD	Other Double	`bytes`	`bytes`
OF	Other Float	`bytes`	`bytes`
OL	Other Long	`bytes`	`bytes`
OV	Other 64-bit Very Long	`bytes`	`bytes`
OW	Other Word	`bytes`	`bytes`
PN	Person Name	`str`	`PersonName`	Union[None, T, MutableSequence[T]]
SH	Short String	`str`	`str`
SL	Signed Long	`int`	`int`
SQ	Sequence of Items	`list`	`Sequence`	MutableSequence[ `Dataset`]
SS	Signed Short	`int`	`int`	Union[None, T, MutableSequence[T]]
ST	Short Text	`str`	`str`	Optional[T]
SV	Signed 64-bit Very Long	`int`	`int`	Union[None, T, MutableSequence[T]]
TM	Time	`str`	`str` or `TM`²
UC	Unlimited Characters	`str`	`str`
UI	Unique Identifier (UID)	`str`	`UID`
UL	Unsigned Long	`int`	`int`
UN	Unknown	`bytes`	`bytes`	Optional[T]
UR	URI/URL	`str`	`str`	Optional[T]
US	Unsigned Short	`int`	`int`	Union[None, T, MutableSequence[T]]
UT	Unlimited Text	`str`	`str`	Optional[T]
UV	Unsigned 64-bit Very Long	`int`	`int`	Union[None, T, MutableSequence[T]]

1 Any type accepted by Tag() can be used
2 If config.datetime_conversion
= True (default False)
3 If config.use_DS_decimal
= True (default False)