lena.context.Context.formatter is now private. Context attributes can…

… be got and set with dot notation.

lena/context/context.py

@@ -31,6 +31,11 @@ def __init__(self, d=None, formatter=None):
         which should accept a dictionary and return a string.
         The default is ``json.dumps``.
 
+        All public attributes of a :class:`Context`
+        can be got or set using dot notation
+        (for example, *context["data_path"]*
+        is equal to *context.data_path*).
+
         Tip
         ---
             JSON and Python representations are different.
@@ -39,6 +44,10 @@ def __init__(self, d=None, formatter=None):
 
         If *formatter* is given but is not callable,
         :exc:`.LenaTypeError` is raised.
+        If the attribute to be got is missing,
+        :exc:`.LenaAttributeError` is raised.
+        An attempt to get a private attribute raises
+        :exc:`AttributeError`.
         """
         # todo: maybe add intersphinx reference to json
         if d is None:
@@ -50,14 +59,13 @@ def __init__(self, d=None, formatter=None):
                     "formatter must be callable, "
                     "{} given".format(formatter)
                 )
-            self.formatter = formatter
+            self._formatter = formatter
         else:
-            self.formatter = lambda s: json.dumps(s, sort_keys=True, indent=4)
+            self._formatter = lambda s: json.dumps(s, sort_keys=True, indent=4)
+        # formatter should better be private,
+        # otherwise it'll mess with other attributes
         # self.formatter = pprint.PrettyPrinter(indent=1)
 
-    def __repr__(self):
-        return self.formatter(self)
-
     def __call__(self, value):
         """Convert *value*'s context to :class:`Context` on the fly.
 
@@ -72,3 +80,29 @@ def __call__(self, value):
         """
         data, context = lena.flow.get_data_context(value)
         return (data, Context(context))
+
+    def __getattr__(self, name):
+        # see comment for Variable
+        if name.startswith('_'):
+            # this is not LenaAttributeError,
+            # as it wouldn't be so for other Lena classes
+            # that don't implement __getattr__
+            raise AttributeError(name)
+        try:
+            return self[name]
+        except KeyError:
+            raise lena.core.LenaAttributeError(
+                "{} missing".format(name)
+            )
+
+    def __repr__(self):
+        return self._formatter(self)
+
+    def __setattr__(self, attr, value):
+        if attr in ["_formatter"]:
+            # from https://stackoverflow.com/a/17020163/952234
+            super(Context, self).__setattr__(attr, value)
+        elif attr.startswith('_'):
+            raise AttributeError(attr)
+        else:
+            self[attr] = value

tests/context/test_context.py

@@ -1,5 +1,6 @@
 from __future__ import print_function
 
+import copy
 import json
 import pytest
 
@@ -28,3 +29,19 @@ def test_context():
     # Context can also be accepted
     res = c((1, Context()))
     assert res[1] == Context({})
+
+    ## attribute access
+    d1 = copy.deepcopy(d)
+    c = Context(d1)
+    assert c.a == d["a"]
+    # missing attributes raise
+    with pytest.raises(lena.core.LenaAttributeError):
+        c.b
+    c.b = 3
+    d1["b"] = 3
+    assert c == d1
+    # private attributes raise
+    with pytest.raises(AttributeError):
+        c._aaa = 3
+    with pytest.raises(AttributeError):
+        c._aaa