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xmlschema
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.. xmlschema-introduction-start

The *xmlschema* library is an implementation of `XML Schema <http://www.w3.org/2001/XMLSchema>`_
for Python (supports Python 2.7 and Python 3.5+).

This library arises from the needs of a solid Python layer for processing XML
Schema based files for
`MaX (Materials design at the Exascale) <http://www.max-centre.eu>`_  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.

The full `xmlschema documentation is available on "Read the Docs" <http://xmlschema.readthedocs.io/en/latest/>`_.


Features
========

This library includes the following features:

* Full XSD 1.0 and XSD 1.1 support
* Building of XML schema objects from XSD files
* Validation of XML instances against XSD schemas
* Decoding of XML data into Python data and to JSON
* Encoding of Python data and JSON to XML
* Data decoding and encoding ruled by converter classes
* An XPath based API for finding schema's elements and attributes
* Support of XSD validation modes *strict*/*lax*/*skip*
* Remote attacks protection by default using an XMLParser that forbids entities

.. note::
    Currently the XSD 1.1 validator is provided by class `XMLSchema11` and
    the default `XMLSchema` class is still an alias of the XSD 1.0 validator,
    the class `XMLSchema10`. From version 1.1 of the package the default
    validator will be linked to the XSD 1.1 validator, a version that will also
    removes support for Python 2.7.


Installation
============

You can install the library with *pip* in a Python 2.7 or Python 3.5+ environment::

    pip install xmlschema

The library uses the Python's ElementTree XML library and requires
`elementpath <https://github.com/brunato/elementpath>`_ additional package.
The base schemas of the XSD standards are included in the package for working
offline and to speed-up the building of schema instances.

.. xmlschema-introduction-end


Usage
=====

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

.. code-block:: pycon

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

.. note::
    For XSD 1.1 schemas use the class `XMLSchema11`, because the default class
    `XMLSchema` is still an alias of the XSD 1.0 validator class `XMLSchema10`.
    From next minor release (v1.1) the default class will become `XMLSchema11`.

The schema can be used to validate XML documents:

.. code-block:: pycon

    >>> my_schema.is_valid('xmlschema/tests/cases/examples/vehicles/vehicles.xml')
    True
    >>> my_schema.is_valid('xmlschema/tests/cases/examples/vehicles/vehicles-1_error.xml')
    False
    >>> my_schema.validate('xmlschema/tests/cases/examples/vehicles/vehicles-1_error.xml')
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/home/brunato/Development/projects/xmlschema/xmlschema/validators/xsdbase.py", line 393, in validate
        raise error
    xmlschema.validators.exceptions.XMLSchemaValidationError: failed validating <Element '{http://example.com/vehicles}cars' at 0x7f8032768458> with XsdGroup(model='sequence').

    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:

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

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

.. code-block:: pycon

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


Authors
=======
Davide Brunato and others who have contributed with code or with sample cases.

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.