Parsing non-standard date element using xmlschema

Question

I have an xsd schema file, which include the following definition:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
...
<xs:element name="CreateDate" minOccurs="0" maxOccurs="1">
    <xs:simpleType>
        <xs:restriction base="xs:string">
            <xs:minLength value="8"/>
            <xs:maxLength value="10"/>
        </xs:restriction>
    </xs:simpleType>
</xs:element>
...

And an xml file which includes the following element:

<?xml version="1.0" encoding="utf-8"?>
...
<!-- format is: YYYY/dd/mm -->
<CreateDate>2020/10/22</CreateDate>
...

I'm using xmlschema to parse the xml file like so:

schema = xmlschema.XMLSchema(schema_file)
element = schema.to_dict(xml_file, datetime_types=True)

Obviously, CreateDate is parsed to a string instead of a Date object. Questions:

1. Is it possible to change the xsd definition, so that xmlschema automatically parses CreateDate to Date using format "YYYY/mm/dd"?
2. If not, I guess I need intercept the parsing using value_hook or element_hook arguments to to_dict(), but I'm not sure how to go about it. Any suggestions?

Answer 1

I only find the hook option on iter_decode, here is an example that just assumes a single element schema and instance:

from pprint import pprint

import xmlschema

from elementpath import datatypes

from datetime import datetime

schema = xmlschema.XMLSchema('schema1.xsd')

def my_element_hook(elementData, xsdElement, xsdType):
    thisDate = datetime.strptime(elementData.text, '%Y/%m/%d')
    return xmlschema.ElementData(tag=elementData.tag,text=datatypes.Date10(thisDate.year, thisDate.month, thisDate.day),attributes=None,content=None)


for value in schema.iter_decode('sample1.xml',datetime_types=True,element_hook=my_element_hook):
    pprint(value)

For a sample sample1.xml like

<?xml version="1.0" encoding="utf-8"?>
<!-- format is: YYYY/mm/dd -->
<CreateDate>2020/10/22</CreateDate>

and a schema

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

<xs:element name="CreateDate">
    <xs:simpleType>
        <xs:restriction base="xs:string">
            <xs:minLength value="8"/>
            <xs:maxLength value="10"/>
        </xs:restriction>
    </xs:simpleType>
</xs:element>

</xs:schema>

I get e.g. Date10(2020, 10, 22).

For a more complex schema I guess the element hook needs to return elementData unchanged for the elements you don't want to manipulate and then for e.g. elementData.tag = 'CreateDate' use the presented code e.g.

def my_element_hook(elementData, xsdElement, xsdType):
    if elementData.tag == 'CreateDate':
        thisDate = datetime.strptime(elementData.text, '%Y/%m/%d')
        return xmlschema.ElementData(tag=elementData.tag,text=datatypes.Date10(thisDate.year, thisDate.month, thisDate.day),attributes=None,content=None)
    else:
        return elementData