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An XML Schema validator and decoder

Project description

This package is an implementation of XML Schema for Python (supports versions 2.7 and Python 3.3+).

This is a library that arises from the needs of a solid Python layer for processing XML Schema based files for MaX (Materials design at the Exascale) European project. A significant problem is the encoding and the decoding of the XML data files produced by different simulation software. Another important requirement is the XML data validation, in order to put the produced data under control. The lack of a suitable alternative for Python in the schema-based decoding of XML data has led to build this library. Obviously this library can be useful for other cases related to XML Schema based processing, not only for the original scope.

Features

The xmlschema library includes the following features:

  • Builds XML schema objects from XSD files

  • Validates the XML instances with the XSD schema

  • Converts XML instances into Python nested dictionaries

  • Provides decoding and encoding APIs for XML’s elements and attributes

Installation

You can install the library with pip in a Python 2.7 or Python 3.3+ environment:

pip install xmlschema

The library uses the Python’s ElementTree XML library and doesn’t require additional packages. The library includes also the schemas of the XML Schema standards for working offline and to speed-up the building of schema instances.

Usage

Import the library and then create an instance of a schema using the path of the file containing the schema as argument:

>>> import xmlschema
>>> my_schema = xmlschema.XMLSchema('xmlschema/tests/examples/vehicles/vehicles.xsd')

The schema can be used to validate XML documents:

>>> my_schema.is_valid('xmlschema/tests/examples/vehicles/vehicles.xml')
True
>>> my_schema.is_valid('xmlschema/tests/examples/vehicles/vehicles-1_error.xml')
False
>>> my_schema.validate('xmlschema/tests/examples/vehicles/vehicles-1_error.xml')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/brunato/Development/projects/xmlschema/xmlschema/schema.py", line 220, in validate
    raise error
xmlschema.exceptions.XMLSchemaValidationError: failed validating <Element ...

Reason: character data between child elements not allowed!

Schema:

  <xs:sequence xmlns:xs="http://www.w3.org/2001/XMLSchema">
        <xs:element maxOccurs="unbounded" minOccurs="0" name="car" type="vh:vehicleType" />
  </xs:sequence>

Instance:

  <ns0:cars xmlns:ns0="http://example.com/vehicles">
    NOT ALLOWED CHARACTER DATA
    <ns0:car make="Porsche" model="911" />
    <ns0:car make="Porsche" model="911" />
  </ns0:cars>

Using a schema you can also decode the XML documents to nested dictionaries, with values that corresponds to the data types declared by the schema:

>>> import xmlschema
>>> from pprint import pprint
>>> xs = xmlschema.XMLSchema('xmlschema/tests/examples/collection/collection.xsd')
>>> pprint(xs.to_dict('xmlschema/tests/examples/collection/collection.xml'))
{u'@xsi:schemaLocation': 'http://example.com/ns/collection collection.xsd',
 'object': [{'@available': True,
             '@id': u'b0836217462',
             'author': {'@id': u'PAR',
                        'born': u'1841-02-25',
                        'dead': u'1919-12-03',
                        'name': u'Pierre-Auguste Renoir',
                        'qualification': u'painter'},
             'estimation': Decimal('10000.00'),
             'position': 1,
             'title': u'The Umbrellas',
             'year': u'1886'},
            {'@available': True,
             '@id': u'b0836217463',
             'author': {'@id': u'JM',
                        'born': u'1893-04-20',
                        'dead': u'1983-12-25',
                        'name': u'Joan Mir\xf3',
                        'qualification': u'painter, sculptor and ceramicist'},
             'position': 2,
             'title': None,
             'year': u'1925'}]}

License

This software is distributed under the terms of the MIT License. See the file ‘LICENSE’ in the root directory of the present distribution, or http://opensource.org/licenses/MIT.

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