If you are using Python to process large HL7 messages and you need to build a long string value for a table field from the values contained in one or more segments of your message, it is best to use an array to build the string.

To use an array to build a string, start by defining a array variable in your Global Inbound script:

myArrayVariable = []

Next, add the following Segment Inbound script in every field that you want to append to the string:

myArrayVariable.append(value + '\n')
# replace '\n' with ' ' if you want to use spaces
# instead of newline characters to separate
# the segment values

This creates a new element of the myArrayVariable array variable. (Recall that the value variable contains the value of a field of a segment.)

Finally, in the Table Inbound script for the table field, create your long string value by joining all of the elements of myArrayVariable together:

value = ''.join(myArrayVariable)

This efficiently creates the long string value for your table field.

	If you are building a long string value, you should avoid code that is similar to the following: myLongStringVariable = myLongStringVariable + value + '\n' To execute this code, Python allocates a new chunk of memory and copies the string to it before appending value. This means that the time required to append to the string increases at a quadratic (n-squared) rate. If the string is very long, your Python script will be noticeably slow, and it may crash due to excessive memory consumption.