Why is there no functional xml?

[Peter Otten]

Rustom Mody wrote:

> Its obviously easier in python to put optional/vararg parameters on the
> right side rather than on the left of a parameter list.
> But its not impossible to get it in the desired order — one just has to
> 'hand-parse' the parameter list received as a *param
> Thusly:

> appointments = E.appointments(
>    {"reminder":"15"},
>    E.appointment(
>         E.begin(1181251680),
>         E.uid("040000008200E000"),
>         E.alarmTime(1181572063),
>         E.state(),
>         E.location(),
>         E.duration(1800),
>         E.subject("Bring pizza home")
>     )
> )

Let's not waste too much effort on minor aesthic improvements ;)

>> Personally I'd probably avoid the extra layer and write a function that
>> directly maps dataclasses or database records to xml using the
>> conventional elementtree API.
> 
> I dont understand…
> [I find the OO/imperative style of making a half-done node and then
> [throwing
> piece-by-piece of contents in/at it highly aggravating]

What I meant is that once you throw a bit of introspection at it much of the 
tedium vanishes. Here's what might become of the DOM-creation as part of an 
actual script:

import xml.etree.ElementTree as xml
from collections import namedtuple

Appointment = namedtuple(
    "Appointment",
    "begin uid alarmTime state location duration subject"
)

appointments = [
    Appointment(
        begin=1181251680,
        uid="040000008200E000",
        alarmTime=1181572063,
        state=None,
        location=None,
        duration=1800,
        subject="Bring pizza home"
    )
]

def create_dom(appointments, reminder):
    node = xml.Element("zAppointments", reminder=str(reminder))
    for appointment in appointments:
        for name, value in zip(appointment._fields, appointment):
            child = xml.SubElement(node, name)
            if value is not None:
                child.text = str(value)
    return node

with open("appt.xml", "wb") as outstream:
    root = create_dom(appointments, 15)
    xml.ElementTree(root).write(outstream)

To generalize that to handle arbitrarily nested lists and namedtuples a bit 
more effort is needed, but I can't see where lxml.objectify could make that 
much easier.