sync to Atlas repo

interfaces/tombola_subhook.py

@@ -0,0 +1,64 @@
+"""
+Variation of ``tombola.Tombola`` implementing ``__subclasshook__``.
+
+Tests with simple classes::
+
+    >>> Tombola.__subclasshook__(object)
+    NotImplemented
+    >>> class Complete:
+    ...     def __init__(): pass
+    ...     def load(): pass
+    ...     def pick(): pass
+    ...     def loaded(): pass
+    ...
+    >>> Tombola.__subclasshook__(Complete)
+    True
+    >>> issubclass(Complete, Tombola)
+
+"""
+
+
+from abc import ABC, abstractmethod
+from inspect import getmembers, isfunction
+
+
+class Tombola(ABC):  # <1>
+
+    @abstractmethod
+    def __init__(self, iterable):  # <2>
+        """New instance is loaded from an iterable."""
+
+    @abstractmethod
+    def load(self, iterable):
+        """Add items from an iterable."""
+
+    @abstractmethod
+    def pick(self):  # <3>
+        """Remove item at random, returning it.
+
+        This method should raise `LookupError` when the instance is empty.
+        """
+
+    def loaded(self):  # <4>
+        try:
+            item = self.pick()
+        except LookupError:
+            return False
+        else:
+            self.load([item])  # put it back
+            return True
+
+    @classmethod
+    def __subclasshook__(cls, other_cls):
+        if cls is Tombola:
+            interface_names = function_names(cls)
+            found_names = set()
+            for a_cls in other_cls.__mro__:
+                found_names |= function_names(a_cls)
+            if found_names >= interface_names:
+                return True
+        return NotImplemented
+
+
+def function_names(obj):
+    return {name for name, _ in getmembers(obj, isfunction)}