# -*- coding: utf-8 -*-
# Copyright (C) 2009 John Paulett (john -at- 7oars.com)
# All rights reserved.
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution.
"""Simple library for parsing messages of Health Level 7 (HL7)
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. Specically, 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\r'
We call the `hl7.parse()` command with string message:
>>> h = parse(message)
We get a hl7.Message object, wrapping a series of hl7.Segment
We can always get the HL7 message back.
>>> str(h) == message.strip()
Interestingly, this hl7.Message can be accessed as a list.
>>> isinstance(h, list)
There were 4 segments (MSH, PID, OBR, OBX):
We can extract the hl7.Segment from the hl7.Message instance.
[['OBX'], ['1'], ['SN'], ['1554-5', 'GLUCOSE', 'POST 12H CFST:MCNC:PT:SER/PLAS:QN'], [''], ['', '182'], ['mg/dl'], ['70_105'], ['H'], [''], [''], ['F']]
We can easily reconstitute this segment as HL7, using the
'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:
We can look up segments by the segment identifer:
>>> pid = segment('PID', h)
Project site: http://www.bitbucket.org/johnpaulett/python-hl7/wiki/Home
__version__ = '0.1.0a'
__author__ = 'John Paulett'
__email__ = 'john -at- 7oars.com'
__license__ = 'BSD'
__copyright__ = 'Copyright 2009, John Paulett <john -at- 7oars.com>'
__url__ = 'http://www.bitbucket.org/johnpaulett/python-hl7/wiki/Home'
"""Determines whether a *line* looks like an HL7 message.
This method only does a cursory check and does not fully
validate the message.
## Prevent issues if the line is empty
return line.strip().startswith('MSH') if line else False
def segment(segment_id, message):
"""Gets the first segment with the *segment_id* from the parsed *message*.
>>> segment('OBX', [[['OBR'],['1']], [['OBX'], ['1']], [['OBX'], ['2']]])
## Get the list of all the segments and pull out the first one if possible
match = segments(segment_id, message)
## Make sure we won't get an IndexError
return match if match else None
def segments(segment_id, message):
"""Returns the requested segments from the parsed *message* that are identified
by the *segment_id* (e.g. OBR, MSH, ORC, OBX).
>>> segments('OBX', [[['OBR'], ['1']], [['OBX'], ['1']], [['OBX'], ['2']]])
[[['OBX'], ['1']], [['OBX'], ['2']]]
## Compare segment_id to the very first string in each segment, returning
## all segments that match
return [segment for segment in message if segment == segment_id]
"""Returns a instance of the Message class that allows indexed access
to the data elements.
>>> message = 'MSH|^~\&|GHH LAB|ELAB-3|'
>>> h = parse(message)
>>> str(h) == message
## Strip out unnecessary whitespace
strmsg = line.strip()
## The method for parsing the message
plan = create_parse_plan(strmsg)
## Start spliting the methods based upon the ParsePlan
return _split(strmsg, plan)
def _split(text, plan):
"""Recursive function to split the *text* into an n-deep list,
according to the :cls:`hl7._ParsePlan`.
## Base condition, if we have used up all the plans
if not plan:
## Recurse so that the sub plans are used in order to split the data
## into the approriate type as defined by the current plan.
data = [_split(x, plan.next()) for x in text.split(plan.separator)]
## Return the instance of the current message part according
## to the plan
"""Abstract root class for the parts of the HL7 message."""
def __init__(self, separator, sequence=):
## Initialize the list object, optionally passing in the
## sequence. Since list() == , using the default
## parameter will not cause any issues.
self.separator = separator
## Join a the child containers into a single string, separated
## by the self.separator. This method acts recursively, calling
## the children's __str__ method. Thus str() is the approriate
## method for turning the python-hl7 representation of HL7 into
## a standard string
return self.separator.join((str(x) for x in self))
"""Representation of an HL7 message. It contains a list
of :cls:`hl7.Segment` instances.
#def __getitem__(self, key):
# return None
"""Second level of an HL7 message, which represents an HL7 Segment.
Traditionally this is a line of a message that ends with a carriage
return and is separated by pipes. It contains a list of
"""Third level of an HL7 message, that traditionally is surrounded
by pipes and separated by carets. It contains a list of strings.
"""Creates a plan on how to parse the HL7 message according to
the details stored within the message.
## We will always use a carriage return to separate segments
separators = ['\r']
## Parse out the other separators from the characters following
## MSH. Currently we only go two-levels deep and ignore some
## The ordered list of containers to create
containers = [Message, Segment, Field]
return _ParsePlan(separators, containers)
"""Details on how to parse an HL7 message. Typically this object
should be created via :func:`hl7.create_parse_plan`
# field, component, repetition, escape, subcomponent
# TODO implement escape, and subcomponent
def __init__(self, separators, containers):
# TODO test to see performance implications of the assertion
# since we generate the ParsePlan, this should never be in
# invalid state
assert len(containers) == len(separators)
self.separators = separators
self.containers = containers
"""Return the current separator to use based on the plan."""
def container(self, data):
"""Return an instance of the approriate container for the *data*
as specified by the current plan.
return self.containers(self.separator, data)
"""Generate the next level of the plan (essentially generates
a copy of this plan with the level of the container and the
seperator starting at the next index.
if len(self.containers) > 1:
## Return a new instance of this class using the tails of
## the separators and containers lists. Use self.__class__()
## in case :cls:`hl7.ParsePlan` is subclassed
return self.__class__(self.separators[1:], self.containers[1:])
## When we have no separators and containers left, return None,
## which indicates that we have nothing further.