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<div class="section" id="module-apache_beam.typehints.typehints">
<span id="apache-beam-typehints-typehints-module"></span><h1>apache_beam.typehints.typehints module<a class="headerlink" href="#module-apache_beam.typehints.typehints" title="Permalink to this headline"></a></h1>
<p>Syntax &amp; semantics for type-hinting custom-functions/PTransforms in the SDK.</p>
<p>This module defines type-hinting objects and the corresponding syntax for
type-hinting function arguments, function return types, or PTransform object
themselves. TypeHint’s defined in the module can be used to implement either
static or run-time type-checking in regular Python code.</p>
<p>Type-hints are defined by ‘indexing’ a type-parameter into a defined
CompositeTypeHint instance:</p>
<blockquote>
<div><ul class="simple">
<li>‘List[int]’.</li>
</ul>
</div></blockquote>
<p>Valid type-hints are partitioned into two categories: simple, and composite.</p>
<p>Simple type hints are type hints based on a subset of Python primitive types:
int, bool, float, str, object, None, and bytes. No other primitive types are
allowed.</p>
<p>Composite type-hints are reserved for hinting the types of container-like
Python objects such as ‘list’. Composite type-hints can be parameterized by an
inner simple or composite type-hint, using the ‘indexing’ syntax. In order to
avoid conflicting with the namespace of the built-in container types, when
specifying this category of type-hints, the first letter should capitalized.
The following composite type-hints are permitted. NOTE: ‘T’ can be any of the
type-hints listed or a simple Python type:</p>
<blockquote>
<div><ul class="simple">
<li>Any</li>
<li>Union[T, T, T]</li>
<li>Optional[T]</li>
<li>Tuple[T, T]</li>
<li>Tuple[T, …]</li>
<li>List[T]</li>
<li>KV[T, T]</li>
<li>Dict[T, T]</li>
<li>Set[T]</li>
<li>Iterable[T]</li>
<li>Iterator[T]</li>
<li>Generator[T]</li>
</ul>
</div></blockquote>
<p>Type-hints can be nested, allowing one to define type-hints for complex types:</p>
<blockquote>
<div><ul class="simple">
<li>‘List[Tuple[int, int, str]]</li>
</ul>
</div></blockquote>
<p>In addition, type-hints can be used to implement run-time type-checking via the
‘type_check’ method on each TypeConstraint.</p>
<dl class="class">
<dt id="apache_beam.typehints.typehints.TypeVariable">
<em class="property">class </em><code class="descclassname">apache_beam.typehints.typehints.</code><code class="descname">TypeVariable</code><span class="sig-paren">(</span><em>name</em><span class="sig-paren">)</span><a class="reference internal" href="_modules/apache_beam/typehints/typehints.html#TypeVariable"><span class="viewcode-link">[source]</span></a><a class="headerlink" href="#apache_beam.typehints.typehints.TypeVariable" title="Permalink to this definition"></a></dt>
<dd><p>Bases: <code class="xref py py-class docutils literal"><span class="pre">apache_beam.typehints.typehints.AnyTypeConstraint</span></code></p>
<dl class="method">
<dt id="apache_beam.typehints.typehints.TypeVariable.match_type_variables">
<code class="descname">match_type_variables</code><span class="sig-paren">(</span><em>concrete_type</em><span class="sig-paren">)</span><a class="reference internal" href="_modules/apache_beam/typehints/typehints.html#TypeVariable.match_type_variables"><span class="viewcode-link">[source]</span></a><a class="headerlink" href="#apache_beam.typehints.typehints.TypeVariable.match_type_variables" title="Permalink to this definition"></a></dt>
<dd></dd></dl>
<dl class="method">
<dt id="apache_beam.typehints.typehints.TypeVariable.bind_type_variables">
<code class="descname">bind_type_variables</code><span class="sig-paren">(</span><em>bindings</em><span class="sig-paren">)</span><a class="reference internal" href="_modules/apache_beam/typehints/typehints.html#TypeVariable.bind_type_variables"><span class="viewcode-link">[source]</span></a><a class="headerlink" href="#apache_beam.typehints.typehints.TypeVariable.bind_type_variables" title="Permalink to this definition"></a></dt>
<dd></dd></dl>
</dd></dl>
<dl class="attribute">
<dt id="apache_beam.typehints.typehints.WindowedValue">
<code class="descclassname">apache_beam.typehints.typehints.</code><code class="descname">WindowedValue</code><a class="headerlink" href="#apache_beam.typehints.typehints.WindowedValue" title="Permalink to this definition"></a></dt>
<dd><p>alias of <code class="xref py py-class docutils literal"><span class="pre">WindowedTypeConstraint</span></code></p>
</dd></dl>
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