Repeated Elements Transformation XML to CSV, Python 3

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import lxml.etree as et

xml_str = '''<ProjectData>
                <FINAL>
                    <START id="ID0001" service_code="0x5196">
                      <Docs Docs_type="START">
                        <Rational>225196</Rational>
                        <Qualify>6251960000A0DE</Qualify>
                      </Docs>
                      <Description num="1213f2312">The parameter</Description>
                      <DataFile dg="12" dg_id="let">
                        <SetData value="32" />
                      </DataFile>
                    </START>
                    <START id="DG0003" service_code="0x517B">
                      <Docs Docs_type="START">
                        <Rational>23423</Rational>
                        <Qualify>342342</Qualify>
                      </Docs>
                      <Description num="3423423f3423">The third</Description>
                      <DataFile dg="55" dg_id="big">
                        <SetData x="E1" value="21259" />
                        <SetData x="E2" value="02" />
                      </DataFile>
                    </START>
                    <START id="ID0048" service_code="0x5198">
                      <RawData rawdata_type="ASDS">
                        <Rational>225198</Rational>
                        <Qualify>343243324234234</Qualify>
                      </RawData>
                      <Description num="434234234">The forth</Description>
                      <DataFile unit="21" unit_id="FEDS">
                        <SetData xin="5" xax="233" value="323" />
                        <SetData xin="123" xax="77" value="555" />
                        <SetData xin="17" xax="65" value="23" />
                      </DataFile>
                    </START>
                </FINAL>
             </ProjectData>'''

xsl_str = '''<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
              <xsl:output indent="yes" method="text"/>
              <xsl:strip-space elements="*"/>

<xsl:variable name="delim">,</xsl:variable>
              <xsl:template match="/ProjectData">
                  <xsl:text>id,service_code,rational,qualify,description_num,description,</xsl:text>
                  <xsl:text>data_file_dg,data_file_dg_id,data_file_unit,data_file_unit_id,</xsl:text>
                  <xsl:text>set_data_x,set_data_xin,set_data_xat,set_data_value&#xa;</xsl:text>
                  <xsl:apply-templates select="descendant::SetData"/>
              </xsl:template>

<xsl:template match="SetData">
                  <xsl:value-of select="concat(ancestor::START/@id, $delim,
                                               ancestor::START/@service_code, $delim,
                                               ancestor::START/*[1]/Rational, $delim,
                                               ancestor::START/*[1]/Qualify, $delim,
                                               ancestor::START/Description/@num, $delim,
                                               ancestor::START/Description, $delim,
                                               ancestor::START/DataFile/@dg, $delim,
                                               ancestor::START/DataFile/@dg_id, $delim,
                                               ancestor::START/DataFile/@unit, $delim,
                                               ancestor::START/DataFile/@unit_id, $delim,
                                               @x, $delim,
                                               @xin, $delim,
                                               @xat, $delim,
                                               @value)"/>
                  <xsl:text>&#xa;</xsl:text>
              </xsl:template>

</xsl:stylesheet>'''

# LOAD XML AND XSL
xml = et.fromstring(xml_str)
xsl = et.fromstring(xsl_str)

# RUN TRANSFORMATION
transformer = et.XSLT(xsl)
result = transformer(xml)

print(str(result))

[ + ] Show input
Absolute running time: 0.19 sec, cpu time: 0.17 sec, memory peak: 11 Mb, absolute service time: 0,2 sec