Add compose, partialable and xpath to resources/python.

resources/python/partialable.py

@@ -0,0 +1,42 @@
+import inspect
+
+
+class n_partialable(object):
+
+    @staticmethod
+    def arity_evaluation_checker(function):
+        function_info = inspect.getargspec(function)
+        function_args = function_info.args
+        if inspect.isclass(function):
+            # This is to handle the fact that self will get passed in automatically.
+            function_args = function_args[1:]
+        def evaluation_checker(*args, **kwargs):
+            acceptable_kwargs = function_args[len(args):]
+            kwarg_keys = set(kwargs.keys())
+            # Make sure that we didn't get an argument we can't handle.
+            assert kwarg_keys.issubset(acceptable_kwargs)
+            needed_args = function_args[len(args):]
+            if function_info.defaults:
+                needed_args = needed_args[:-len(function_info.defaults)]
+            return not needed_args or kwarg_keys.issuperset(needed_args)
+        return evaluation_checker
+
+    def __init__(self, function, evaluation_checker=None, args=None, kwargs=None):
+        self.function = function
+        self.evaluation_checker = (evaluation_checker or
+                                   self.arity_evaluation_checker(function))
+        self.args = args or ()
+        self.kwargs = kwargs or {}
+
+    def __call__(self, *args, **kwargs):
+        new_args = self.args + args
+        new_kwargs = self.kwargs.copy()
+        new_kwargs.update(kwargs)
+        if self.evaluation_checker(*new_args, **new_kwargs):
+            return self.function(*new_args, **new_kwargs)
+        else:
+            return type(self)(self.function, self.evaluation_checker,
+                              new_args, new_kwargs)
+
+
+n_partialable = n_partialable(n_partialable)