**Each abstract base class specifies a set of virtual subclasses. These classes are then recognized by isinstance() and issubclass() as subclasses of the ABC, although they are really not. ABC can also manually decide whether or not a specific class is its virtual subclass, usually based on which methods the class has implemented. For instance, Iterable ABC looks for method iter() while Collection ABC looks for methods iter(), contains() and len().**
**Each abstract base class specifies a set of virtual subclasses. These classes are then recognized by isinstance() and issubclass() as subclasses of the ABC, although they are really not. ABC can also manually decide whether or not a specific class is its virtual subclass, usually based on which methods the class has implemented. For instance, Iterable ABC looks for method iter(), while Collection ABC looks for iter(), contains() and len().**
```python
>>> from collections.abc import Iterable, Collection, Sequence
<div><h4id="sometypesdonothavebuiltinnamessotheymustbeimported">Some types do not have built-in names, so they must be imported:</h4><pre><codeclass="python language-python hljs"><spanclass="hljs-keyword">from</span> types <spanclass="hljs-keyword">import</span> FunctionType, MethodType, LambdaType, GeneratorType, ModuleType
</code></pre></div>
<div><h3id="abstractbaseclasses">Abstract Base Classes</h3><p><strong>Each abstract base class specifies a set of virtual subclasses. These classes are then recognized by isinstance() and issubclass() as subclasses of the ABC, although they are really not. ABC can also manually decide whether or not a specific class is its virtual subclass, usually based on which methods the class has implemented. For instance, Iterable ABC looks for method iter() while Collection ABC looks for methods iter(), contains() and len().</strong></p><pre><codeclass="python language-python hljs"><spanclass="hljs-meta">>>></span><spanclass="hljs-keyword">from</span> collections.abc <spanclass="hljs-keyword">import</span> Iterable, Collection, Sequence
<div><h3id="abstractbaseclasses">Abstract Base Classes</h3><p><strong>Each abstract base class specifies a set of virtual subclasses. These classes are then recognized by isinstance() and issubclass() as subclasses of the ABC, although they are really not. ABC can also manually decide whether or not a specific class is its virtual subclass, usually based on which methods the class has implemented. For instance, Iterable ABC looks for method iter(), while Collection ABC looks for iter(), contains() and len().</strong></p><pre><codeclass="python language-python hljs"><spanclass="hljs-meta">>>></span><spanclass="hljs-keyword">from</span> collections.abc <spanclass="hljs-keyword">import</span> Iterable, Collection, Sequence