Initial implementation of variants

Author: pganssle

src/variants/__init__.py

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+# -*- coding: utf-8 -*-
+
+"""Top-level package for variants."""
+
+from ._variants import variants
+
+__author__ = """Paul Ganssle"""
+__version__ = '0.1.0'
+
+__all__ = ['variants']

src/variants/_variants.py

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+# -*- coding: utf-8 -*-
+"""Provides the variant form decorator."""
+
+import six
+
+import types
+
+__all__ = ['variants']
+
+
+class _StaticCallableMetaclass(type):
+    """Metaclass for a static callable function."""
+
+    def __call__(cls, *args, **kwargs):
+        """Rather than calling the constructor, call a static function."""
+        return cls.__main_form__(*args, **kwargs)
+
+    def __repr__(cls):
+        return cls.__func_repr__()
+
+
+def variants(f):
+    """
+    Decorator to register a function that has variant forms.
+
+    Decorate the main form of the function with this decorator, and then
+    subsequent variants should be declared with the same name as the original
+    function.
+
+    .. example::
+
+        @variants
+        def myfunc(fpath):
+            with open(fpath, 'r') as f:
+                do_something(f.read())
+
+        @myfunc.variant('from_url') as f:
+        def myfunc(url):
+            r = requests.get(url)
+            do_something(r.text)
+    """
+
+    @six.add_metaclass(_StaticCallableMetaclass)
+    class VariantFunction:
+        __doc__ = f.__doc__
+
+        @staticmethod
+        def __main_form__(*args, **kwargs):
+            return f(*args, **kwargs)
+
+        @classmethod
+        def variant(cls, func_name):
+            def decorator(vfunc):
+                setattr(cls, func_name, vfunc)
+                return cls
+
+            return decorator
+
+        @classmethod
+        def __func_repr__(cls):
+            return '<VariantFunction {}>'.format(cls.__name__)
+
+    VariantFunction.__name__ = f.__name__
+
+    return VariantFunction