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<div class="section" id="using-binding-classes">
<span id="usebind"></span><h1>Using Binding Classes<a class="headerlink" href="#using-binding-classes" title="Permalink to this headline">¶</a></h1>
<p>Python instances corresponding to XML structures can be created in two
primary ways: from XML documents, and directly within Python code.
Generating XML documents from bindings can also be controlled.</p>
<div class="section" id="creating-instances-from-xml-documents">
<span id="from-xml"></span><h2>Creating Instances from XML Documents<a class="headerlink" href="#creating-instances-from-xml-documents" title="Permalink to this headline">¶</a></h2>
<p>XML documents are converted into Python bindings by invoking the
<tt class="docutils literal"><span class="pre">CreateFromDocument</span></tt> function in a binding module. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">po3</span>
<span class="n">order</span> <span class="o">=</span> <span class="n">po3</span><span class="o">.</span><span class="n">CreateFromDocument</span><span class="p">(</span><span class="nb">file</span><span class="p">(</span><span class="s">'po3.xml'</span><span class="p">)</span><span class="o">.</span><span class="n">read</span><span class="p">())</span>
<span class="k">print</span> <span class="s">'</span><span class="si">%s</span><span class="s"> is sending </span><span class="si">%s</span><span class="s"> </span><span class="si">%d</span><span class="s"> thing(s):'</span> <span class="o">%</span> <span class="p">(</span><span class="n">order</span><span class="o">.</span><span class="n">billTo</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">order</span><span class="o">.</span><span class="n">shipTo</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="n">order</span><span class="o">.</span><span class="n">items</span><span class="o">.</span><span class="n">item</span><span class="p">))</span>
<span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">order</span><span class="o">.</span><span class="n">items</span><span class="o">.</span><span class="n">item</span><span class="p">:</span>
<span class="k">print</span> <span class="s">' Quantity </span><span class="si">%d</span><span class="s"> of </span><span class="si">%s</span><span class="s"> at $</span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">item</span><span class="o">.</span><span class="n">quantity</span><span class="p">,</span> <span class="n">item</span><span class="o">.</span><span class="n">productName</span><span class="p">,</span> <span class="n">item</span><span class="o">.</span><span class="n">USPrice</span><span class="p">)</span>
</pre></div>
</div>
<p>The <tt class="docutils literal"><span class="pre">CreateFromDocument</span></tt> function in a given binding module is configured
so that documents with no default namespace are assumed to be in the
namespace from which the binding was generated.</p>
<div class="section" id="locating-invalid-content">
<span id="invalid-content"></span><h3>Locating Invalid Content<a class="headerlink" href="#locating-invalid-content" title="Permalink to this headline">¶</a></h3>
<p>If a document does not validate, PyXB will generally through an
<a class="reference external" href="api/pyxb-module.html#UnrecognizedContentError">UnrecognizedContentError</a> exception. You can determine where the
problem lies, and what was not recognized, by examining attributes present
on the exception as shown in this example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">pyxb</span>
<span class="kn">import</span> <span class="nn">po1</span>
<span class="n">xml</span> <span class="o">=</span> <span class="nb">file</span><span class="p">(</span><span class="s">'badcontent.xml'</span><span class="p">)</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">order</span> <span class="o">=</span> <span class="n">po1</span><span class="o">.</span><span class="n">CreateFromDocument</span><span class="p">(</span><span class="n">xml</span><span class="p">,</span> <span class="n">location_base</span><span class="o">=</span><span class="s">'badcontent.xml'</span><span class="p">)</span>
<span class="k">except</span> <span class="n">pyxb</span><span class="o">.</span><span class="n">UnrecognizedContentError</span><span class="p">,</span> <span class="n">e</span><span class="p">:</span>
<span class="k">print</span> <span class="s">'Unrecognized element "</span><span class="si">%s</span><span class="s">" at </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="p">(</span><span class="n">e</span><span class="o">.</span><span class="n">content</span><span class="o">.</span><span class="n">expanded_name</span><span class="p">,</span> <span class="n">e</span><span class="o">.</span><span class="n">content</span><span class="o">.</span><span class="n">location</span><span class="p">)</span>
</pre></div>
</div>
<p>which produces:</p>
<div class="highlight-python"><pre>Unrecognized element "streeet" at badcontent.xml[5:4]
</pre>
</div>
</div>
<div class="section" id="coping-with-wrong-xsi-type-attributes">
<h3>Coping With Wrong <tt class="docutils literal"><span class="pre">xsi:type</span></tt> Attributes<a class="headerlink" href="#coping-with-wrong-xsi-type-attributes" title="Permalink to this headline">¶</a></h3>
<p>Some web services and binding tools mis-use <a class="reference external" href="http://www.w3.org/TR/xmlschema-1/#xsi_type">xsi:type</a>, providing attribute values
that either are not types, or do not specify a type that is derived from an
abstract type. The
<a class="reference external" href="api/pyxb.namespace.builtin._XMLSchema_instance-class.html#ProcessTypeAttribute">pyxb.namespace.builtin.XMLSchema_instance.ProcessTypeAttribute</a> method
can be used to relax how PyXB processes those attributes.</p>
</div>
</div>
<div class="section" id="creating-instances-in-python-code">
<span id="from-python"></span><h2>Creating Instances in Python Code<a class="headerlink" href="#creating-instances-in-python-code" title="Permalink to this headline">¶</a></h2>
<p>Creating bindings from XML documents is straightforward, because the
documents contain enough information to identify each element and attribute,
locate the corresponding use in the binding class, and store a value that is
converted to the appropriate type. Creating values in Python is inherently
more complex, because native Python objects like strings and integers do not
contain this information.</p>
<p>As described in <a class="reference external" href="arch_binding.html#bindingmodel"><em>Binding Model</em></a>, binding classes corresponding to simple
types extend the underlying Python type (such as <tt class="docutils literal"><span class="pre">str</span></tt> or <tt class="docutils literal"><span class="pre">int</span></tt>), and
add XML-specific information like the canonical representation of the value
in <a class="reference external" href="http://www.unicode.org/">Unicode</a>, which is the natural representation
as XML text. These classes also maintain a set of facets that constrain the
values that can be stored as instances when validation is active. Binding
classes for complex types have constructors that parse positional and
keyword parameters to determine the appropriate element or attribute to
which the value belongs. Attributes are assigned using keyword parameters.
Content is assigned using positional parameters. The order of the
positional parameters must be consistent with the order expected by the
content model.</p>
<p>Using the schema in the <a class="reference external" href="userref_pyxbgen.html#nsaddress-xsd"><em>namespace-aware address schema</em></a>, we can begin to construct the example document in Python:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">address</span>
<span class="n">addr</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">()</span>
<span class="n">addr</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s">'Robert Smith'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">street</span> <span class="o">=</span> <span class="s">'8 Oak Avenue'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">city</span> <span class="o">=</span> <span class="s">'Anytown'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">state</span> <span class="o">=</span> <span class="s">'AK'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">zip</span> <span class="o">=</span> <span class="mi">12341</span>
<span class="k">print</span> <span class="n">addr</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>This produces:</p>
<div class="highlight-python"><pre><?xml version="1.0" ?><ns1:USAddress xmlns:ns1="URN:address"><name>Robert Smith</name><street>8 Oak Avenue</street><city>Anytown</city><state>AK</state><zip>12341</zip></ns1:USAddress>
</pre>
</div>
<p>Assigning to individual fields like this bypasses the complex type content
model, although each field itself is validated. For example, the address
schema does not include New York as a state, so the following assignment:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">addr</span><span class="o">.</span><span class="n">state</span> <span class="o">=</span> <span class="s">'NY'</span>
</pre></div>
</div>
<p>will cause a <a class="reference external" href="api/pyxb.exceptions_.BadTypeValueError-class.html">BadTypeValueError</a> exception to be raised:</p>
<div class="highlight-python"><pre>Traceback (most recent call last):
File "demo4a1.py", line 7, in <module>
addr.state = 'NY'
File "/home/pab/pyxb/dev/pyxb/binding/basis.py", line 62, in __setattr__
return super(_TypeBinding_mixin, self).__setattr__(name, value)
File "/home/pab/pyxb/dev/pyxb/binding/content.py", line 399, in set
value = self.__elementBinding.compatibleValue(value, is_plural=self.isPlural())
File "/home/pab/pyxb/dev/pyxb/binding/basis.py", line 1331, in compatibleValue
return self.typeDefinition()._CompatibleValue(value, **kw)
File "/home/pab/pyxb/dev/pyxb/binding/basis.py", line 270, in _CompatibleValue
return cls(value)
File "/home/pab/pyxb/dev/pyxb/binding/basis.py", line 712, in __init__
self.xsdConstraintsOK()
File "/home/pab/pyxb/dev/pyxb/binding/basis.py", line 845, in xsdConstraintsOK
return self.XsdConstraintsOK(self)
File "/home/pab/pyxb/dev/pyxb/binding/basis.py", line 839, in XsdConstraintsOK
raise pyxb.BadTypeValueError('%s violation for %s in %s' % (f.Name(), value, cls.__name__))
pyxb.exceptions_.BadTypeValueError: enumeration violation for NY in USState
</pre>
</div>
<p>However, the order of the field assignments does not matter, as long as all
required fields are present by the time the XML document is generated.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">address</span>
<span class="n">addr</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">()</span>
<span class="n">addr</span><span class="o">.</span><span class="n">street</span> <span class="o">=</span> <span class="s">'8 Oak Avenue'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">state</span> <span class="o">=</span> <span class="s">'AK'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">city</span> <span class="o">=</span> <span class="s">'Anytown'</span>
<span class="n">addr</span><span class="o">.</span><span class="n">zip</span> <span class="o">=</span> <span class="mi">12341</span>
<span class="n">addr</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s">'Robert Smith'</span>
<span class="k">print</span> <span class="n">addr</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>Alternatively, you can provide the content as positional parameters in the
object creation call:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="c"># examples/manual/demo4b.py</span>
<span class="kn">import</span> <span class="nn">address</span>
<span class="n">addr</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Robert Smith'</span><span class="p">,</span> <span class="s">'8 Oak Avenue'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="k">print</span> <span class="n">addr</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>This has the same effect, and is much more compact, but it does require that
the order match the content model.</p>
<p>Attributes are set using keyword parameters:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="c"># examples/manual/demo4c.py</span>
<span class="kn">import</span> <span class="nn">pyxb</span>
<span class="kn">import</span> <span class="nn">po4</span>
<span class="kn">import</span> <span class="nn">address</span>
<span class="kn">import</span> <span class="nn">pyxb.binding.datatypes</span> <span class="kn">as</span> <span class="nn">xs</span>
<span class="n">po</span> <span class="o">=</span> <span class="n">po4</span><span class="o">.</span><span class="n">purchaseOrder</span><span class="p">(</span><span class="n">orderDate</span><span class="o">=</span><span class="n">xs</span><span class="o">.</span><span class="n">date</span><span class="p">(</span><span class="mi">1999</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">20</span><span class="p">))</span>
<span class="n">po</span><span class="o">.</span><span class="n">shipTo</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Alice Smith'</span><span class="p">,</span> <span class="s">'123 Maple Street'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="n">po</span><span class="o">.</span><span class="n">billTo</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Robert Smith'</span><span class="p">,</span> <span class="s">'8 Oak Avenue'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="n">pyxb</span><span class="o">.</span><span class="n">RequireValidWhenGenerating</span><span class="p">(</span><span class="bp">False</span><span class="p">)</span>
<span class="k">print</span> <span class="n">po</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>This example produces (after reformatting):</p>
<div class="highlight-python"><pre><?xml version="1.0"?>
<ns1:purchaseOrder xmlns:ns1="URN:purchase-order" orderDate="1999-10-20">
<ns1:billTo>
<city>Anytown</city>
<state>AK</state>
<street>8 Oak Avenue</street>
<name>Robert Smith</name>
<zip>12341</zip>
</ns1:billTo>
<ns1:shipTo>
<city>Anytown</city>
<state>AK</state>
<street>123 Maple Street</street>
<name>Alice Smith</name>
<zip>12341</zip>
</ns1:shipTo>
</ns1:purchaseOrder>
</pre>
</div>
<p id="index-6">Note that, because we’re in the middle of the example and have not provided
the <tt class="docutils literal"><span class="pre">items</span></tt> element that the content model requires, the code
<a class="reference external" href="api/pyxb-module.html#RequireValidWhenGenerating">explicitly disables the requirement for
validation</a> when generating XML from a
binding instance. A consequence of this is that the generated XML is not
valid, and validation must be <a class="reference external" href="api/pyxb-module.html#RequireValidWhenParsing">disabled for parsing</a> as well if the resulting document is to be
re-converted into a binding with <tt class="docutils literal"><span class="pre">CreateFromDocument</span></tt>.</p>
<div class="section" id="creating-instances-of-anonymous-types">
<h3>Creating Instances of Anonymous Types<a class="headerlink" href="#creating-instances-of-anonymous-types" title="Permalink to this headline">¶</a></h3>
<p>The style of XML schema used for purchase orders uses anonymous types for
the deeper elements of the purchase order:</p>
<div class="highlight-python"><pre><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="URN:purchase-order"
xmlns:tns="URN:purchase-order"
xmlns:address="URN:address"
elementFormDefault="qualified">
<xsd:import namespace="URN:address" schemaLocation="nsaddress.xsd"/>
<xsd:element name="purchaseOrder" type="tns:PurchaseOrderType"/>
<xsd:element name="comment" type="xsd:string"/>
<xsd:complexType name="PurchaseOrderType">
<xsd:sequence>
<xsd:element name="shipTo" type="address:USAddress"/>
<xsd:element name="billTo" type="address:USAddress"/>
<xsd:element ref="tns:comment" minOccurs="0"/>
<xsd:element name="items" type="tns:Items"/>
</xsd:sequence>
<xsd:attribute name="orderDate" type="xsd:date"/>
</xsd:complexType>
<xsd:complexType name="Items">
<xsd:sequence>
<xsd:element name="item" minOccurs="0" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="productName" type="xsd:string"/>
<xsd:element name="quantity">
<xsd:simpleType>
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxExclusive value="100"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
<xsd:element name="USPrice" type="xsd:decimal"/>
<xsd:element ref="tns:comment" minOccurs="0"/>
<xsd:element name="shipDate" type="xsd:date" minOccurs="0"/>
</xsd:sequence>
<xsd:attribute name="partNum" type="tns:SKU" use="required"/>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
<!-- Stock Keeping Unit, a code for identifying products -->
<xsd:simpleType name="SKU">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\d{3}-[A-Z]{2}"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:schema>
</pre>
</div>
<p id="index-7">In particular, there is no global <tt class="docutils literal"><span class="pre">item</span></tt> element that can be used to
create the individual items. For situations like this, we use
<a class="reference external" href="api/pyxb.BIND-class.html">BIND</a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">pyxb</span>
<span class="kn">import</span> <span class="nn">po4</span>
<span class="kn">import</span> <span class="nn">address</span>
<span class="kn">import</span> <span class="nn">pyxb.binding.datatypes</span> <span class="kn">as</span> <span class="nn">xs</span>
<span class="n">po</span> <span class="o">=</span> <span class="n">po4</span><span class="o">.</span><span class="n">purchaseOrder</span><span class="p">(</span><span class="n">orderDate</span><span class="o">=</span><span class="n">xs</span><span class="o">.</span><span class="n">date</span><span class="p">(</span><span class="mi">1999</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">20</span><span class="p">))</span>
<span class="n">po</span><span class="o">.</span><span class="n">shipTo</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Alice Smith'</span><span class="p">,</span> <span class="s">'123 Maple Street'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="n">po</span><span class="o">.</span><span class="n">billTo</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Robert Smith'</span><span class="p">,</span> <span class="s">'8 Oak Avenue'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="n">po</span><span class="o">.</span><span class="n">items</span> <span class="o">=</span> <span class="n">pyxb</span><span class="o">.</span><span class="n">BIND</span><span class="p">(</span><span class="n">pyxb</span><span class="o">.</span><span class="n">BIND</span><span class="p">(</span><span class="s">'Lapis necklace'</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mf">99.95</span><span class="p">,</span> <span class="n">partNum</span><span class="o">=</span><span class="s">'833-AA'</span><span class="p">),</span>
<span class="n">pyxb</span><span class="o">.</span><span class="n">BIND</span><span class="p">(</span><span class="s">'Plastic necklace'</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mf">3.95</span><span class="p">,</span> <span class="n">partNum</span><span class="o">=</span><span class="s">'833-AB'</span><span class="p">))</span>
<span class="k">print</span> <span class="n">po</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>The <a class="reference external" href="api/pyxb.BIND-class.html">BIND</a> reference wraps the content of the inner elements, and
is a cue to PyXB to attempt to build an instance of whatever type of object
would satisfy the content model at that point. The resulting document
(after reformatting) is:</p>
<div class="highlight-python"><pre><?xml version="1.0"?>
<ns1:purchaseOrder xmlns:ns1="URN:purchase-order" orderDate="1999-10-20">
<ns1:shipTo>
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Anytown</city>
<state>AK</state>
<zip>12341</zip>
</ns1:shipTo>
<ns1:billTo>
<name>Robert Smith</name>
<street>8 Oak Avenue</street>
<city>Anytown</city>
<state>AK</state>
<zip>12341</zip>
</ns1:billTo>
<ns1:items>
<ns1:item partNum="833-AA">
<ns1:productName>Lapis necklace</ns1:productName>
<ns1:quantity>1</ns1:quantity>
<ns1:USPrice>99.95</ns1:USPrice>
</ns1:item>
<ns1:item partNum="833-AB">
<ns1:productName>Plastic necklace</ns1:productName>
<ns1:quantity>4</ns1:quantity>
<ns1:USPrice>3.95</ns1:USPrice>
</ns1:item>
</ns1:items>
</ns1:purchaseOrder>
</pre>
</div>
<p>The complete document is generated by the following program:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">pyxb</span>
<span class="kn">import</span> <span class="nn">po4</span>
<span class="kn">import</span> <span class="nn">address</span>
<span class="kn">import</span> <span class="nn">pyxb.binding.datatypes</span> <span class="kn">as</span> <span class="nn">xs</span>
<span class="kn">import</span> <span class="nn">datetime</span>
<span class="n">po</span> <span class="o">=</span> <span class="n">po4</span><span class="o">.</span><span class="n">purchaseOrder</span><span class="p">(</span><span class="n">orderDate</span><span class="o">=</span><span class="n">xs</span><span class="o">.</span><span class="n">date</span><span class="p">(</span><span class="mi">1999</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">20</span><span class="p">))</span>
<span class="n">po</span><span class="o">.</span><span class="n">shipTo</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Alice Smith'</span><span class="p">,</span> <span class="s">'123 Maple Street'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="n">po</span><span class="o">.</span><span class="n">billTo</span> <span class="o">=</span> <span class="n">address</span><span class="o">.</span><span class="n">USAddress</span><span class="p">(</span><span class="s">'Robert Smith'</span><span class="p">,</span> <span class="s">'8 Oak Avenue'</span><span class="p">,</span> <span class="s">'Anytown'</span><span class="p">,</span> <span class="s">'AK'</span><span class="p">,</span> <span class="mi">12341</span><span class="p">)</span>
<span class="n">po</span><span class="o">.</span><span class="n">items</span> <span class="o">=</span> <span class="n">pyxb</span><span class="o">.</span><span class="n">BIND</span><span class="p">(</span><span class="n">pyxb</span><span class="o">.</span><span class="n">BIND</span><span class="p">(</span><span class="s">'Lapis necklace'</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mf">99.95</span><span class="p">,</span> <span class="n">partNum</span><span class="o">=</span><span class="s">'833-AA'</span><span class="p">),</span>
<span class="n">pyxb</span><span class="o">.</span><span class="n">BIND</span><span class="p">(</span><span class="s">'Plastic necklace'</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mf">3.95</span><span class="p">,</span> <span class="n">partNum</span><span class="o">=</span><span class="s">'833-AB'</span><span class="p">))</span>
<span class="n">po</span><span class="o">.</span><span class="n">shipTo</span><span class="o">.</span><span class="n">country</span> <span class="o">=</span> <span class="n">po</span><span class="o">.</span><span class="n">billTo</span><span class="o">.</span><span class="n">country</span> <span class="o">=</span> <span class="n">po</span><span class="o">.</span><span class="n">shipTo</span><span class="o">.</span><span class="n">country</span>
<span class="n">lapis</span> <span class="o">=</span> <span class="n">po</span><span class="o">.</span><span class="n">items</span><span class="o">.</span><span class="n">item</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="n">lapis</span><span class="o">.</span><span class="n">shipDate</span> <span class="o">=</span> <span class="n">po</span><span class="o">.</span><span class="n">orderDate</span> <span class="o">+</span> <span class="n">datetime</span><span class="o">.</span><span class="n">timedelta</span><span class="p">(</span><span class="n">days</span><span class="o">=</span><span class="mi">46</span><span class="p">)</span>
<span class="n">lapis</span><span class="o">.</span><span class="n">comment</span> <span class="o">=</span> <span class="s">'Want this for the holidays!'</span>
<span class="n">po</span><span class="o">.</span><span class="n">items</span><span class="o">.</span><span class="n">item</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">shipDate</span> <span class="o">=</span> <span class="n">po</span><span class="o">.</span><span class="n">items</span><span class="o">.</span><span class="n">item</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">shipDate</span> <span class="o">+</span> <span class="n">datetime</span><span class="o">.</span><span class="n">timedelta</span><span class="p">(</span><span class="n">days</span><span class="o">=</span><span class="mi">19</span><span class="p">)</span>
<span class="k">print</span> <span class="n">po</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>The additional code demonstrates a couple additional features:</p>
<blockquote>
<ul class="simple">
<li>Fixed attribute values (such as <tt class="docutils literal"><span class="pre">country</span></tt>) are present in the bindings,
even though they are only printed if they are set explicitly</li>
<li>The PyXB types for representing dates and times are extensions of those
used by Python for the same purpose, including the ability to use them in
expressions</li>
</ul>
</blockquote>
</div>
</div>
<div class="section" id="creating-xml-documents-from-binding-instances">
<span id="to-xml"></span><h2>Creating XML Documents from Binding Instances<a class="headerlink" href="#creating-xml-documents-from-binding-instances" title="Permalink to this headline">¶</a></h2>
<p>All along we’ve been seeing how to generate XML from a binding instance.
The <tt class="docutils literal"><span class="pre">toxml</span></tt> method is short-hand for a sequence that converts the binding
to a DOM instance using <tt class="docutils literal"><span class="pre">xml.dom.minidom</span></tt>, then uses the DOM interface to
generate the XML document.</p>
<p>The <a class="reference external" href="api/pyxb.utils.domutils.BindingDOMSupport-class.html">BindingDOMSupport</a> class provides ways to
control this generation. In particular, you may want to use something more
informative than <tt class="docutils literal"><span class="pre">ns#</span></tt> to denote namespaces in the generated documents.
This can be done using the following code:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">pyxb.utils.domutils</span>
<span class="n">pyxb</span><span class="o">.</span><span class="n">utils</span><span class="o">.</span><span class="n">domutils</span><span class="o">.</span><span class="n">BindingDOMSupport</span><span class="o">.</span><span class="n">DeclareNamespace</span><span class="p">(</span><span class="n">address</span><span class="o">.</span><span class="n">Namespace</span><span class="p">,</span> <span class="s">'addr'</span><span class="p">)</span>
<span class="n">pyxb</span><span class="o">.</span><span class="n">utils</span><span class="o">.</span><span class="n">domutils</span><span class="o">.</span><span class="n">BindingDOMSupport</span><span class="o">.</span><span class="n">DeclareNamespace</span><span class="p">(</span><span class="n">po4</span><span class="o">.</span><span class="n">Namespace</span><span class="p">,</span> <span class="s">'po'</span><span class="p">)</span>
<span class="k">print</span> <span class="n">po</span><span class="o">.</span><span class="n">toxml</span><span class="p">()</span>
</pre></div>
</div>
<p>With this, the final document produced is:</p>
<div class="highlight-python"><pre><?xml version="1.0"?>
<po:purchaseOrder xmlns:po="URN:purchase-order" orderDate="1999-10-20">
<po:shipTo country="US">
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Anytown</city>
<state>AK</state>
<zip>12341</zip>
</po:shipTo>
<po:billTo country="US">
<name>Robert Smith</name>
<street>8 Oak Avenue</street>
<city>Anytown</city>
<state>AK</state>
<zip>12341</zip>
</po:billTo>
<po:items>
<po:item partNum="833-AA">
<po:productName>Lapis necklace</po:productName>
<po:quantity>1</po:quantity>
<po:USPrice>99.95</po:USPrice>
<po:comment>Want this for the holidays!</po:comment>
<po:shipDate>1999-12-05</po:shipDate>
</po:item>
<po:item partNum="833-AB">
<po:productName>Plastic necklace</po:productName>
<po:quantity>4</po:quantity>
<po:USPrice>3.95</po:USPrice>
<po:shipDate>1999-12-24</po:shipDate>
</po:item>
</po:items>
</po:purchaseOrder>
</pre>
</div>
<p>(Surprise: <tt class="docutils literal"><span class="pre">addr</span></tt> does not appear, because the <tt class="docutils literal"><span class="pre">nsaddress.xsd</span></tt> schema
uses the default element form <tt class="docutils literal"><span class="pre">unqualified</span></tt>, so none of the address
components in the document have a namespace.)</p>
</div>
</div>
</div>
</div>
</div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference external" href="#">Using Binding Classes</a><ul>
<li><a class="reference external" href="#creating-instances-from-xml-documents">Creating Instances from XML Documents</a><ul>
<li><a class="reference external" href="#locating-invalid-content">Locating Invalid Content</a></li>
<li><a class="reference external" href="#coping-with-wrong-xsi-type-attributes">Coping With Wrong <tt class="docutils literal"><span class="pre">xsi:type</span></tt> Attributes</a></li>
</ul>
</li>
<li><a class="reference external" href="#creating-instances-in-python-code">Creating Instances in Python Code</a><ul>
<li><a class="reference external" href="#creating-instances-of-anonymous-types">Creating Instances of Anonymous Types</a></li>
</ul>
</li>
<li><a class="reference external" href="#creating-xml-documents-from-binding-instances">Creating XML Documents from Binding Instances</a></li>
</ul>
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</ul>
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