Extracting Information From a Message

def get_field(message, segment_index, field_index, subfield_index=None):
   '''Get a particular field (or subfield) from a given segment in a message.
   
   All indexes are one-based, like in the HL7 standard.  E.g., the MSH segment
   is the 1st segment.  As a special case, the name of a segment is considered
   the value of the zero-th field.

   >>> msg = ('MSH|^~\\&|EPIC|EPICADT|SMS|SMSADT|199912271408|CHARRIS|ADT^A04|1817457|D|2.3|\r'
              'EVN|A04|199912271408|||CHARRIS')
   >>> get_field(msg, 1, 9)
   'ADT^A04'
   >>> get_field(msg, 1, 9, 1)
   'ADT'
   '''
   # We need to deal with the one special case: MSH.1 = '|'
   if segment_index == 1:
      if field_index == 1:
         return '|'
      elif field_index > 1:
         field_index -= 1

   segment = message.split('\r', segment_index)[segment_index-1]
   field   = segment.split('|',  field_index+1)[field_index]

   if subfield_index:
      return field.split('^', subfield_index)[subfield_index-1]
   else
      return field

For example, you can use get_field to obtain the message code and trigger event of a message, which are located in subfields 1 and 2 of field 9 of the MSH segment:

message_code  = get_field(value, 1, 9, 1)
trigger_event = get_field(value, 1, 9, 2)

The message code and trigger event are the components of the message's identity.


	If you include this function in the Global Inbound Script of your message definition file, you can use it in any of your Python scripts.

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Extracting Information From a Message