ENH: dispatch(Field, collections.Mapping) for compute_up

blaze/__init__.py

@@ -19,6 +19,7 @@
 import warnings
 from .expr import (
     Symbol,
+    broadcast_collect,
     by,
     cast,
     coalesce,

blaze/compute/python.py

@@ -11,6 +11,7 @@
 """
 from __future__ import absolute_import, division, print_function
 
+from collections import Mapping
 import itertools
 import numbers
 import fnmatch
@@ -768,7 +769,7 @@ def compute_up(expr, seq, **kwargs):
     raise NotImplementedError("Only 1d slices supported")
 
 
-@dispatch(Field, dict)
+@dispatch(Field, Mapping)
 def compute_up(expr, data, **kwargs):
     return data[expr._name]
 

blaze/compute/tests/test_python_compute.py

@@ -1,11 +1,13 @@
 from __future__ import absolute_import, division, print_function
+from collections import Mapping
 
 import math
 import itertools
 import operator
 import pytest
 from datetime import datetime, date
 import datashape
+from datashape.py2help import mappingproxy
 from collections import Iterator, Iterable
 
 import blaze
@@ -834,6 +836,27 @@ def test_compute_field_on_dicts():
     assert compute(s.x, {s: d}) == [1, 2, 3]
 
 
+class _MapProxy(Mapping):  # pragma: no cover
+    def __init__(self, mapping):
+        self._map = mapping
+
+    def __getitem__(self, key):
+        return self._map[key]
+
+    def __iter__(self):
+        return iter(self._map)
+
+    def __len__(self):
+        return len(self._map)
+
+
+@pytest.mark.parametrize('cls', (_MapProxy, mappingproxy))
+def test_comute_on_mapping(cls):
+    s = symbol('s', '{x: 3 * int64, y: 3 * float32}')
+    d = cls({'x': [1, 2, 3], 'y': [4.0, 5.0, 6.0]})
+    assert compute(s.x, {s: d}, return_type='native') == [1, 2, 3]
+
+
 def test_truncate():
     s = symbol('x', 'real')
     assert compute(s.truncate(20), 154) == 140

blaze/expr/broadcast.py

@@ -12,7 +12,7 @@
 from .strings import Like
 from .datetime import DateTime
 
-__all__ = ['broadcast', 'Broadcast', 'scalar_symbols']
+__all__ = ['broadcast', 'Broadcast', 'scalar_symbols', 'broadcast_collect']
 
 
 def broadcast(expr, leaves, scalars=None):

docs/source/whatsnew/0.10.0.txt

@@ -52,6 +52,8 @@ Improved Backends
 
 * Adds :class:`~blaze.expr.math.greatest` and :class:`~blaze.expr.math.least`
   support to the sql backend (:issue:`1428`).
+* Generalize ``Field`` to support :class:`collections.Mapping` object
+  (:issue:`1467`).
 
 Experimental Features
 ~~~~~~~~~~~~~~~~~~~~~