python-hl7 is a simple library for parsing messages of Health Level 7 (HL7) version 2.x into Python objects. python-hl7 includes a simple client that can send HL7 messages to a Minimal Lower Level Protocol (MLLP) server (mllp_send).
HL7 is a communication protocol and message format for health care data. It is the de-facto standard for transmitting data between clinical information systems and between clinical devices. The version 2.x series, which is often is a pipe delimited format is currently the most widely accepted version of HL7 (version 3.0 is an XML-based format).
python-hl7 currently only parses HL7 version 2.x messages into an easy to access data structure. The current implementation does not completely follow the HL7 specification, but is good enough to parse the most commonly seen HL7 messages. The library could potentially evolve into being fully complainant with the spec. The library could eventually also contain the ability to create HL7 v2.x messages.
python-hl7 parses HL7 into a series of wrapped hl7.Container objects. The there are specific subclasses of hl7.Container depending on the part of the HL7 message. The hl7.Container message itself is a subclass of a Python list, thus we can easily access the HL7 message as an n-dimensional list. Specifically, the subclasses of hl7.Container, in order, are hl7.Message, hl7.Segment, and hl7.Field. Eventually additional containers will be added to fully support the HL7 specification.
As an example, let’s create a HL7 message:
>>> message = 'MSH|^~\&|GHH LAB|ELAB-3|GHH OE|BLDG4|200202150930||ORU^R01|CNTRL-3456|P|2.4\r' >>> message += 'PID|||555-44-4444||EVERYWOMAN^EVE^E^^^^L|JONES|196203520|F|||153 FERNWOOD DR.^^STATESVILLE^OH^35292||(206)3345232|(206)752-121||||AC555444444||67-A4335^OH^20030520\r' >>> message += 'OBR|1|845439^GHH OE|1045813^GHH LAB|1554-5^GLUCOSE|||200202150730||||||||555-55-5555^PRIMARY^PATRICIA P^^^^MD^^LEVEL SEVEN HEALTHCARE, INC.|||||||||F||||||444-44-4444^HIPPOCRATES^HOWARD H^^^^MD\r' >>> message += 'OBX|1|SN|1554-5^GLUCOSE^POST 12H CFST:MCNC:PT:SER/PLAS:QN||^182|mg/dl|70_105|H|||F'
We call the hl7.parse() command with string message:
>>> import hl7 >>> h = hl7.parse(message)
>>> type(h) <class 'hl7.Message'>
We can always get the HL7 message back:
>>> unicode(h) == message True
Interestingly, hl7.Message can be accessed as a list:
>>> isinstance(h, list) True
There were 4 segments (MSH, PID, OBR, OBX):
>>> len(h) 4
>>> h [[u'OBX'], [u'1'], [u'SN'], [u'1554-5', u'GLUCOSE', u'POST 12H CFST:MCNC:PT:SER/PLAS:QN'], [u''], [u'', u'182'], [u'mg/dl'], [u'70_105'], [u'H'], [u''], [u''], [u'F']]
We can easily reconstitute this segment as HL7, using the appropriate separators:
>>> unicode(h) u'OBX|1|SN|1554-5^GLUCOSE^POST 12H CFST:MCNC:PT:SER/PLAS:QN||^182|mg/dl|70_105|H|||F'
We can extract individual elements of the message:
>>> h u'GLUCOSE' >>> h u'182'
We can look up segments by the segment identifier, either via hl7.Message.segments() or via the traditional dictionary syntax:
>>> h.segments('OBX') u'GLUCOSE' >>> h['OBX'] u'GLUCOSE'
Since many many types of segments only have a single instance in a message (e.g. PID or MSH), hl7.Message.segment() provides a convienance wrapper around hl7.Message.segments() that returns the first matching hl7.Segment:
>>> h.segment('PID') u'555-44-4444'
python-hl7 features a simple network client, mllp_send, which reads HL7 messages from a file or sys.stdin and posts them to an MLLP server. mllp_send is a command-line wrapper around hl7.client.MLLPClient. mllp_send is a useful tool for testing HL7 interfaces or resending logged messages:
mllp_send --file sample.hl7 --port 6661 mirth.example.com
See mllp_send - MLLP network client for examples and usage instructions.