How to build an xml template with variable attributes from scratch

Question

My goal is to build an xml template with placeholders for variable attributes. for some reasons, the template would not take in new data into its placeholders.

Here's an example:

x=2*5
xmlTemplate="""
<personal reference="500.txt">
    <others:sequence>
        <feature:name="name" age="age" dob="dob"/>
    </others:sequence>
</personal>""".format(name='Michael', age=x, dob=15/10/1900)
print xmlTemplate

Output:

<personal reference="500.txt">
    <others:sequence>
        <feature:name="name" age="age" dob="dob"/>
    </others:sequence>
</personal>

Ideal output:

<personal reference="500.txt">
    <others:sequence>
        <feature:name="Michael" age="10" dob="15/10/1900"/>
    </others:sequence>
</personal>

Any ideas? Thanks.

score 4 · Answer 1 · edited Jan 29 '18 at 22:21

To create an XML document in Python, it seems easier to use the Yattag library.

from yattag import Doc

doc, tag, text = Doc().tagtext()

x = 2*5

with tag('personal', reference = "500.txt"):
    with tag('others:sequence'):
        doc.stag('feature', name = "Michael", age = str(x), dob = "15/10/1900")

print(doc.getvalue())

When run, the above code will generate the following XML:

<personal reference="500.txt">
  <others:sequence>
    <feature name="Michael" age="10" dob="15/10/1900" />
  </others:sequence>
</personal>

Note: Indentation was added to the example above for readability, as getvalue returns a single line without spaces between tags. To produce a formatted document, use the indent function.

unutbu · Accepted Answer · 2014-04-06T18:18:31.183

Your template needs curly braces:

x=2*5
xmlTemplate="""
<personal reference="500.txt">
    <others:sequence>
        <feature:name="{name}" age="{age}" dob="{dob}"/>
    </others:sequence>
</personal>""".format(name='Michael', age=x, dob='15/10/1900')
print xmlTemplate

yields

<personal reference="500.txt">
    <others:sequence>
        <feature:name="Michael" age="10" dob="15/10/1900"/>
    </others:sequence>
</personal>

The format method replaces names in curly-braces. Compare, for example,

In [20]: 'cheese'.format(cheese='Roquefort')
Out[20]: 'cheese'

In [21]: '{cheese}'.format(cheese='Roquefort')
Out[21]: 'Roquefort'

I see you have lxml. Excellent. In that case, you could use lxml.builder to construct XML. This will help you create valid XML:

import lxml.etree as ET
import lxml.builder as builder
E = builder.E
F = builder.ElementMaker(namespace='http://foo', nsmap={'others':'http://foo'})

x = 2*5
xmlTemplate = ET.tostring(F.root(
    E.personal(
        F.sequence(
            E.feature(name='Michael',
                   age=str(x),
                   dob='15/10/1900')
            ), reference="500.txt")),
                          pretty_print=True)
print(xmlTemplate)

yields

<others:root xmlns:other="http://foo">
  <personal reference="500.txt">
    <others:sequence>
      <feature dob="15/10/1900" age="10" name="Michael"/>
    </others:sequence>
  </personal>
</others:root>

and this string can be parsed by lxml using:

doc = ET.fromstring(xmlTemplate)
print(doc)
# <Element {http://foo}root at 0xb741866c>

thank you so much. The first time I put the curly braces without inverted commas, and it didn't work. Then I removed it, I knew all along I needed curly braces but couldn't figure out how to use them. — Tiger1, Apr 06 '14 at 17:28
I'm having problem parsing the output xml. I use **Lxml** and it would not parse. can you give it a try? Thanks. — Tiger1, Apr 06 '14 at 17:42
The namespace prefix `others` needs to be defined. I've added some code above, showing how to define `others` in a root element. — unutbu, Apr 06 '14 at 18:12
Will `.format` account for variables with apostrophes or quotation marks? (`description="Created by \"John Doe\" in 2016"`) — Stevoisiak, Jan 29 '18 at 17:27
@StevenVascellaro: The `str.format` only performs literal string replacement. To automatically [escape quotation marks](https://stackoverflow.com/q/1222367/190597) it is easire to use `lxml.builder`. — unutbu, Jan 29 '18 at 18:02

How to build an xml template with variable attributes from scratch

2 Answers2