Tips for finding prefixed tags in python lxml?

I am trying to using lxml's ElementTree etree to find a specific tag in my xml document. The tag looks as follows:

<text:ageInformation>
    <text:statedAge>12</text:statedAge>
</text:ageInformation>

I was hoping to use etree.find('text:statedAge'), but that method does not like 'text' prefix. It mentions that I should add 'text' to the prefix map, but I am not certain how to do it. Any tips?

Edit: I want to be able to write to the hr4e prefixed tags. Here are the important parts of the document:

<?xml version="1.0" encoding="utf-8"?>
<greenCCD xmlns="AlschulerAssociates::GreenCDA" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:hr4e="hr4e::patientdata" xsi:schemaLocation="AlschulerAssociates::GreenCDA green_ccd.xsd">
  <header>
    <documentID root="18c41e51-5f4d-4d15-993e-2a932fed720a" />
    <title>Health Records for Everyone Continuity of Care Document</title>
    <version>
  <number>1</number>
</version>
<confidentiality codeSystem="2.16.840.1.113883.5.25" code="N" />
<documentTimestamp value="201105300211+0800" />
<personalInformation>
  <patientInformation>
    <personID root="2.16.840.1.113883.3.881.PI13023911" />
    <personAddress>
      <streetAddressLine nullFlavor="NI" />
      <city>Santa Cruz</city>
      <state nullFlavor="NI" />
      <postalCode nullFlavor="NI" />
    </personAddress>
    <personPhone nullFlavor="NI" />
    <personInformation>
      <personName>
        <given>Benjamin</given>
        <family>Keidan</family>
      </personName>
      <gender codeSystem="2.16.840.1.113883.5.1" code="M" />
      <personDateOfBirth value="NI" />
      <hr4e:ageInformation>
        <hr4e:statedAge>9424</hr4e:statedAge>
        <hr4e:estimatedAge>0912</hr4e:estimatedAge>
        <hr4e:ye开发者_运维知识库arInSchool>1</hr4e:yearInSchool>
        <hr4e:statusInSchool>attending</hr4e:statusInSchool>
      </hr4e:ageInformation>
    </personInformation>
    <hr4e:livingSituation>
      <hr4e:homeVillage>Putney</hr4e:homeVillage>
      <hr4e:tribe>Oromo</hr4e:tribe>
    </hr4e:livingSituation>
  </patientInformation>
</personalInformation>

The namespace prefix must be declared (mapped to an URI) in the XML document. Then you can use the {URI}localname notation to find text:statedAge and other elements. Something like this:

from lxml import etree

XML = """
<root xmlns:text="http://example.com">
 <text:ageInformation>
   <text:statedAge>12</text:statedAge>
 </text:ageInformation>
</root>"""

root = etree.fromstring(XML)

ageinfo = root.find("{http://example.com}ageInformation")
age = ageinfo.find("{http://example.com}statedAge")
print age.text

This will print "12".

Another way of doing it:

ageinfo = root.find("text:ageInformation",
                    namespaces={"text": "http://example.com"})
age = ageinfo.find("text:statedAge",
                   namespaces={"text": "http://example.com"})
print age.text

You can also use XPath:

age = root.xpath("//text:statedAge",
                 namespaces={"text": "http://example.com"})[0]
print age.text

I ended up having to use nested prefixes:

from lxml import etree

XML = """
<greenCCD xmlns="AlschulerAssociates::GreenCDA" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:hr4e="hr4e::patientdata"  xsi:schemaLocation="AlschulerAssociates::GreenCDA green_ccd.xsd">
<personInformation>
 <hr4e:ageInformation>
   <hr4e:statedAge>12</hr4e:statedAge>
 </hr4e:ageInformation>
</personInformation>
</greenCCD>"""

root = etree.fromstring(XML)
#root = etree.parse("hr4e_patient.xml")

ageinfo = root.find("{AlschulerAssociates::GreenCDA}personInformation/{hr4e::patientdata}ageInformation")
age = ageinfo.find("{hr4e::patientdata}statedAge")
print age.text