pynetdicom.pdu_items.PresentationContextItemRQ

class pynetdicom.pdu_items.PresentationContextItemRQ

A Presentation Context (RQ) Item.

Presentation Contexts (RQ) Items are used by the association requestor to propose Abstract Syntaxes (specifications of data elements with associated semantics) and Transfer Syntaxes (sets of encoding rules) 1.

abstract_syntax

The Presentation Context Item’s Abstract Syntax (if available).

Type

pydicom.uid.UID or None.

abstract_transfer_syntax_sub_items

The Abstract/Transfer Syntax Sub-Items field value. The order of the items is not guaranteed.

Type

list of AbstractSyntaxSubItem and TransferSyntaxSubItem

item_length

The number of bytes from the first byte following the Item Length field to the last byte of the Item.

Type

int

item_type

The Item Type field value (0x20).

Type

int

presentation_context_id

The Presentation Context ID field value, an odd integer between 1 and 255.

Type

int or None

transfer_syntax

The Presentation Context Item’s Transfer Syntax(es) (if available).

Type

list of pydicom.uid.UID

Notes

A Presentation Context (RQ) Item requires the following parameters:

• Item type (1, fixed value, 0x20)

• Item length (1)

• Presentation context ID (1)

• Abstract/Transfer Syntax Sub-items (1)

  • Abstract Syntax Sub-item (1)

    • Item type (1, fixed, 0x30)

    • Item length (1)

    • Abstract syntax name (1)

  • Transfer Syntax Sub-items (1 or more)

    • Item type (1, fixed, 0x40)

    • Item length (1)

    • Transfer syntax name(s) (1 or more)

Encoding

When encoded, a Presentation Context (RQ) Item has the following structure, taken from Table 9-13 2 (offsets shown with Python indexing). Items are always encoded using Big Endian 3.

Offset	Length	Description
0	1	Item type
1	1	Reserved
2	2	Item length
4	1	Presentation context ID
5	1	Reserved
6	1	Reserved
7	1	Reserved
8	Variable	Abstract/transfer syntax sub-items

References

1

DICOM Standard, Part 8, Annex B

2

DICOM Standard, Part 8, Section 9.3.2.2

3

DICOM Standard, Part 8, Section 9.3.1

__init__()

Initialise a new Presentation Context (RQ) Item.

Methods

__init__()	Initialise a new Presentation Context (RQ) Item.
decode(bytestream)	Decode bytestream and use the result to set the field values of the PDU item.
encode()	Return the encoded PDU as bytes.
from_primitive(primitive)	Set the item's values using a Presentation Context primitive.
to_primitive()	Return a PresentationContext primitive from the current Item.

Attributes

abstract_syntax	Return the Abstract Syntax, if available.
context_id	Return the item's Presentation Context ID field value as an int.
item_length	Return the item's Item Length field value as an int.
item_type	Return the item's Item Type field value as an int.
transfer_syntax	Return the Transfer Syntax(es).