XML & XSLT Example

I really like working with XML and XSLT transformations.  I have used them to create subset data in code for clients.  There is just something simple and beautiful about transforming a base document into another document for another purpose.  Then I saw a job on Guru that required just that.  I thought to myself, I ought to dust off the books and put together a simple command line program to do a transformation in a generic way.  So I did just that and wrote this program:

# Name:        xml xslt processor
# Purpose:     Skill demonstration using lxml technologies
# Author:      Demolishun
# Created:     14/03/2017
# Copyright:   (c) Demolishun 2017
# Licence:     all rights reserved

import os
import sys
import argparse
import lxml.etree as etree

# check input files
def checkinputfiles(args):
    # check files exist
    if not os.path.isfile(args.xml_in) or not os.path.isfile(args.xslt_in):
        return None

    # check if files are xml
    xml_in = None
        xml_in = etree.parse(args.xml_in)
    except etree.XMLSyntaxError, e:
        print "Error processing input xml file: {}".format(args.xml_in)
        return None

    xslt_in = None
        xslt_in = etree.parse(args.xslt_in)
    except etree.XMLSyntaxError, e:
        print "Error processing input xslt file: {}".format(args.xslt_in)
        return None

    return {"xml_in":xml_in, "xslt_in":xslt_in}

# process xml using xslt
def processxml(trees):
    # create transform from xslt
    transform = etree.XSLT(trees["xslt_in"])

    # process xml using transform
    outdoc = transform(trees["xml_in"])

    return outdoc

def main():
    # create argument parser
    parser = argparse.ArgumentParser(description='Convert XML document using XSLT document.')

    # add inputs for arguments

    # parse arguments, close app if correct args are not present
    args = parser.parse_args()

    #print args

    # determine if files are present and are indeed xml files
    trees = checkinputfiles(args)

    if trees == None:
        print "One or more files not found: {}, {}".format(args.xml_in, args.xslt_in)
        return -1

    # process input xml against input xslt
    outdoc = processxml(trees)
    #print outdoc
    #print etree.tostring(outdoc, method="txt", xml_declaration = False) #, pretty_print=True, )
        text_file = open(args.doc_out, "w")
    except Exception as e:
        #print e
        print "Error writing output file: {}".format(args.doc_out)

if __name__ == '__main__':

I then used this source XML document:

<?xml version="1.0"?>


and this XSLT document:

<?xml version="1.0"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
    <xsl:output method="text" omit-xml-declaration="yes" indent="no"/>
    <xsl:template match="/">
        <xsl:for-each select="dataroot/data">
            <xsl:value-of select="name"/> = <xsl:value-of select="trait"/><xsl:text>&#10;</xsl:text>

which transformed into this:

Data1 = red
Data2 = blue
Data3 = yellow
Data4 = blue

It was fun to write and I got some practice doing command line argument processing using a library I had not used yet.  A fun way to exercise some of my skills.  I also now have generic command line processing program to convert XML documents.