Merge 9fce2f8 into d2ab5ed

docs/source/whatsnew/0.9.1.txt

@@ -22,6 +22,13 @@ Enhancements
   factor to only compute over stocks for which the filter returns True, rather
   than always computing over the entire universe of stocks. (:issue:`1095`)
 
+* Implemented :class:`zipline.pipeline.factors.RecarrayFactor`, a new pipeline
+  term designed to be the output type of a CustomFactor with multiple outputs.
+
+* Added optional `outputs` parameter to :class:`zipline.pipeline.CustomFactor`.
+  Custom factors are now capable of computing and returning multiple outputs,
+  each of which are themselves a Factor.
+
 Experimental Features
 ~~~~~~~~~~~~~~~~~~~~~
 

tests/pipeline/test_engine.py

@@ -112,6 +112,16 @@ def compute(self, today, assets, out, open):
         out[:] = open
 
 
+class MultipleOutputs(CustomFactor):
+    window_length = 1
+    inputs = [USEquityPricing.open, USEquityPricing.close]
+    outputs = ['double_open', 'double_close']
+
+    def compute(self, today, assets, out, open, close):
+        out.double_open[:] = open * 2
+        out.double_close[:] = close * 2
+
+
 def assert_multi_index_is_product(testcase, index, *levels):
     """Assert that a MultiIndex contains the product of `*levels`."""
     testcase.assertIsInstance(
@@ -510,6 +520,42 @@ def test_rolling_and_nonrolling(self):
                 ),
             )
 
+    def test_factor_with_multiple_outputs(self):
+        dates = self.dates[5:10]
+        assets = self.assets
+        num_dates = len(dates)
+        open = USEquityPricing.open
+        close = USEquityPricing.close
+        open_values = array([self.constants[open]] * num_dates, dtype=float)
+        close_values = array([self.constants[close]] * num_dates, dtype=float)
+        engine = SimplePipelineEngine(
+            lambda column: self.loader, self.dates, self.asset_finder,
+        )
+
+        double_open, double_close = MultipleOutputs()
+        pipeline = Pipeline(
+            columns={
+                'double_open': double_open,
+                'double_close': double_close,
+            },
+        )
+
+        results = engine.run_pipeline(pipeline, dates[0], dates[-1])
+        first_output_results = results['double_open'].unstack()
+        second_output_results = results['double_close'].unstack()
+
+        first_output_expected = {asset: open_values * 2 for asset in assets}
+        second_output_expected = {asset: close_values * 2 for asset in assets}
+
+        assert_frame_equal(
+            first_output_results,
+            DataFrame(first_output_expected, index=dates, columns=assets),
+        )
+        assert_frame_equal(
+            second_output_results,
+            DataFrame(second_output_expected, index=dates, columns=assets),
+        )
+
     def test_loader_given_multiple_columns(self):
 
         class Loader1DataSet1(DataSet):

zipline/errors.py

@@ -433,10 +433,20 @@ class TermInputsNotSpecified(ZiplineError):
     msg = "{termname} requires inputs, but no inputs list was passed."
 
 
+class TermOutputsNotSpecified(ZiplineError):
+    """
+    Raised if a user attempts to construct a term without specifying outputs
+    and that term does not have class-level default outputs.
+    """
+    msg = (
+        "{termname} requires outputs, but no outputs list was passed."
+    )
+
+
 class WindowLengthNotSpecified(ZiplineError):
     """
-    Raised if a user attempts to construct a term without specifying inputs and
-    that term does not have class-level default inputs.
+    Raised if a user attempts to construct a term without specifying window
+    length and that term does not have a class-level default window length.
     """
     msg = (
         "{termname} requires a window_length, but no window_length was passed."

zipline/pipeline/factors/__init__.py

@@ -1,7 +1,8 @@
 from .factor import (
     CustomFactor,
     Factor,
-    Latest
+    Latest,
+    RecarrayFactor,
 )
 from .events import (
     BusinessDaysSinceCashBuybackAuth,
@@ -44,6 +45,7 @@
     'Latest',
     'MaxDrawdown',
     'RSI',
+    'RecarrayFactor',
     'Returns',
     'SimpleMovingAverage',
     'VWAP',

zipline/pipeline/factors/factor.py

@@ -1,14 +1,14 @@
 """
 factor.py
 """
-from functools import wraps
+from functools import partial, wraps
 from operator import attrgetter
 from numbers import Number
 
 from numpy import inf, where
 from toolz import curry
 
-from zipline.errors import UnknownRankMethod
+from zipline.errors import TermOutputsNotSpecified, UnknownRankMethod
 from zipline.lib.normalize import naive_grouped_rowwise_apply
 from zipline.lib.rank import masked_rankdata_2d
 from zipline.pipeline.classifiers import Classifier, Everything, Quantiles
@@ -1130,8 +1130,13 @@ class CustomFactor(PositiveWindowLengthMixin, CustomTermMixin, Factor):
     inputs : iterable, optional
         An iterable of `BoundColumn` instances (e.g. USEquityPricing.close),
         describing the data to load and pass to `self.compute`.  If this
-        argument is passed to the CustomFactor constructor, we look for a
+        argument is not passed to the CustomFactor constructor, we look for a
         class-level attribute named `inputs`.
+    outputs : iterable, optional
+        An iterable of strings which represent the names of each output this
+        factor should compute and return. If this argument is not passed to the
+        CustomFactor constructor, we look for a class-level attribute named
+        `outputs`.
     window_length : int, optional
         Number of rows to pass for each input.  If this argument is not passed
         to the CustomFactor constructor, we look for a class-level attribute
@@ -1164,7 +1169,9 @@ def compute(self, today, assets, out, *inputs):
             Column labels for `out` and`inputs`.
         out : np.array[self.dtype, ndim=1]
             Output array of the same shape as `assets`.  `compute` should write
-            its desired return values into `out`.
+            its desired return values into `out`. If multiple outputs are
+            specified, `compute` should write its desired return values into
+            `out.<output_name>` for each output name in `self.outputs`.
         *inputs : tuple of np.array
             Raw data arrays corresponding to the values of `self.inputs`.
 
@@ -1229,9 +1236,73 @@ def compute(self, today, assets, out, data):
         # MedianValue.
         median_close10 = MedianValue([USEquityPricing.close], window_length=10)
         median_low15 = MedianValue([USEquityPricing.low], window_length=15)
+
+    A CustomFactor with multiple outputs:
+
+    .. code-block:: python
+
+        class MultipleOutputs(CustomFactor):
+            inputs = [USEquityPricing.close]
+            outputs = ['alpha', 'beta']
+            window_length = N
+
+            def compute(self, today, assets, out, close):
+                computed_alpha, computed_beta = some_function(close)
+                out.alpha = computed_alpha
+                out.beta = computed_beta
+
+        # Each output is returned as its own Factor upon instantiation.
+        alpha, beta = MultipleOutputs()
     '''
     dtype = float64_dtype
 
+    def __getattr__(self, name):
+        if name in self.outputs:
+            return RecarrayFactor(factor=self, attribute=name)
+        else:
+            raise AttributeError(
+                "This factor has no output called '{}'.".format(name)
+            )
+
+    def __iter__(self):
+        if len(self.outputs) < 2:
+            raise ValueError('This factor does not have multiple outputs.')
+        RecarrayFactor_ = partial(RecarrayFactor, self)
+        return iter(map(RecarrayFactor_, self.outputs))
+
+
+class RecarrayFactor(SingleInputMixin, Factor):
+
+    def __new__(cls, factor, attribute):
+        return super(RecarrayFactor, cls).__new__(
+            cls,
+            attribute=attribute,
+            inputs=[factor],
+            outputs=factor.outputs,
+            window_length=0,
+            dtype=factor.dtype,
+            missing_value=factor.missing_value,
+        )
+
+    def _init(self, attribute, *args, **kwargs):
+        self.attribute = attribute
+        return super(RecarrayFactor, self)._init(*args, **kwargs)
+
+    @classmethod
+    def static_identity(cls, attribute, *args, **kwargs):
+        return (
+            super(RecarrayFactor, cls).static_identity(*args, **kwargs),
+            attribute,
+        )
+
+    def _validate(self):
+        super(RecarrayFactor, self)._validate()
+        if not self.outputs:
+            raise TermOutputsNotSpecified(termname=type(self).__name__)
+
+    def _compute(self, windows, dates, assets, mask):
+        return windows[0][self.attribute]
+
 
 class Latest(LatestMixin, CustomFactor):
     """

zipline/pipeline/mixins.py

@@ -1,7 +1,7 @@
 """
 Mixins classes for use with Filters and Factors.
 """
-from numpy import full_like
+from numpy import array, full_like, recarray
 
 from zipline.utils.control_flow import nullctx
 from zipline.errors import WindowLengthNotPositive, UnsupportedDataType
@@ -69,6 +69,7 @@ class CustomTermMixin(object):
 
     def __new__(cls,
                 inputs=NotSpecified,
+                outputs=NotSpecified,
                 window_length=NotSpecified,
                 mask=NotSpecified,
                 dtype=NotSpecified,
@@ -88,6 +89,7 @@ def __new__(cls,
         return super(CustomTermMixin, cls).__new__(
             cls,
             inputs=inputs,
+            outputs=outputs,
             window_length=window_length,
             mask=mask,
             dtype=dtype,
@@ -109,7 +111,14 @@ def _compute(self, windows, dates, assets, mask):
         compute = self.compute
         missing_value = self.missing_value
         params = self.params
-        out = full_like(mask, missing_value, dtype=self.dtype)
+        outputs = self.outputs
+        if outputs:
+            out = recarray(
+                mask.shape, dtype=zip(outputs, [self.dtype] * len(outputs)),
+            )
+            out[:] = array([missing_value])
+        else:
+            out = full_like(mask, missing_value, dtype=self.dtype)
         with self.ctx:
             # TODO: Consider pre-filtering columns that are all-nan at each
             # time-step?

zipline/pipeline/term.py

@@ -349,11 +349,13 @@ class ComputableTerm(Term):
     :class:`zipline.pipeline.Filter`, and :class:`zipline.pipeline.Factor`.
     """
     inputs = NotSpecified
+    outputs = NotSpecified
     window_length = NotSpecified
     mask = NotSpecified
 
     def __new__(cls,
                 inputs=inputs,
+                outputs=outputs,
                 window_length=window_length,
                 mask=mask,
                 *args, **kwargs):
@@ -368,6 +370,13 @@ def __new__(cls,
             # normalize to a tuple so that inputs is hashable.
             inputs = tuple(inputs)
 
+        if outputs is NotSpecified:
+            outputs = cls.outputs
+        if outputs is NotSpecified:
+            outputs = ()
+        else:
+            outputs = tuple(outputs)
+
         if mask is NotSpecified:
             mask = cls.mask
         if mask is NotSpecified:
@@ -379,22 +388,31 @@ def __new__(cls,
         return super(ComputableTerm, cls).__new__(
             cls,
             inputs=inputs,
+            outputs=outputs,
             mask=mask,
             window_length=window_length,
             *args, **kwargs
         )
 
-    def _init(self, inputs, window_length, mask, *args, **kwargs):
+    def _init(self, inputs, outputs, window_length, mask, *args, **kwargs):
         self.inputs = inputs
+        self.outputs = outputs
         self.window_length = window_length
         self.mask = mask
         return super(ComputableTerm, self)._init(*args, **kwargs)
 
     @classmethod
-    def static_identity(cls, inputs, window_length, mask, *args, **kwargs):
+    def static_identity(cls,
+                        inputs,
+                        outputs,
+                        window_length,
+                        mask,
+                        *args,
+                        **kwargs):
         return (
             super(ComputableTerm, cls).static_identity(*args, **kwargs),
             inputs,
+            outputs,
             window_length,
             mask,
         )