WPI: Eval with some PyTables support

pandas/__init__.py

@@ -29,6 +29,7 @@
 from pandas.stats.api import *
 from pandas.tseries.api import *
 from pandas.io.api import *
+from pandas.computation.api import *
 
 from pandas.util.testing import debug
 

pandas/computation/align.py

@@ -0,0 +1,219 @@
+from functools import partial, wraps
+from itertools import izip
+
+import numpy as np
+
+import pandas as pd
+import pandas.core.common as com
+from pandas.computation.ops import is_const
+from pandas.computation.common import flatten
+
+
+def _align_core_single_unary_op(term):
+    if isinstance(term.value, np.ndarray) and not com.is_series(term.value):
+        typ = partial(np.asanyarray, dtype=term.value.dtype)
+    else:
+        typ = type(term.value)
+    ret = typ,
+
+    if not hasattr(term.value, 'axes'):
+        ret += None,
+    else:
+        ret += _zip_axes_from_type(typ, term.value.axes),
+    return ret
+
+
+def _zip_axes_from_type(typ, new_axes):
+    axes = {}
+    for ax_ind, ax_name in typ._AXIS_NAMES.iteritems():
+        axes[ax_name] = new_axes[ax_ind]
+    return axes
+
+
+def _maybe_promote_shape(values, naxes):
+    # test to see if we have an array else leave since must be a number
+    if not isinstance(values, np.ndarray):
+        return values
+
+    ndims = values.ndim
+    if ndims > naxes:
+        raise AssertionError('cannot have more dims than axes, '
+                             '{0} > {1}'.format(ndims, naxes))
+    if ndims == naxes:
+        return values
+
+    ndim = set(xrange(ndims))
+    nax = set(xrange(naxes))
+
+    axes_slice = [slice(None)] * naxes
+
+    # symmetric difference of numaxes and ndims
+    slices = nax - ndim
+
+    if ndims == naxes:
+        if slices:
+            raise AssertionError('slices should be empty if ndims == naxes '
+                                 '{0}'.format(slices))
+    else:
+        if not slices:
+            raise AssertionError('slices should NOT be empty if ndim != naxes '
+                                 '{0}'.format(slices))
+
+    for sl in slices:
+        axes_slice[sl] = np.newaxis
+
+    return values[tuple(axes_slice)]
+
+
+def _any_pandas_objects(terms):
+    """Check a sequence of terms for instances of PandasObject."""
+    return any(com.is_pd_obj(term.value) for term in terms)
+
+
+def _filter_special_cases(f):
+    @wraps(f)
+    def wrapper(terms):
+        # single unary operand
+        if len(terms) == 1:
+            return _align_core_single_unary_op(terms[0])
+
+        # only scalars
+        elif all(term.isscalar for term in terms):
+            return np.result_type(*(term.value for term in terms)), None
+
+        # single element ndarrays
+        all_has_size = all(hasattr(term.value, 'size') for term in terms)
+        if (all_has_size and all(term.value.size == 1 for term in terms)):
+            return np.result_type(*(term.value for term in terms)), None
+
+        # no pandas so just punt to the evaluator
+        if not _any_pandas_objects(terms):
+            return np.result_type(*(term.value for term in terms)), None
+
+        return f(terms)
+    return wrapper
+
+
+@_filter_special_cases
+def _align_core(terms):
+    term_index = [i for i, term in enumerate(terms) if hasattr(term.value,
+                                                               'axes')]
+    term_dims = [terms[i].value.ndim for i in term_index]
+    ndims = pd.Series(dict(zip(term_index, term_dims)))
+
+    # initial axes are the axes of the largest-axis'd term
+    biggest = terms[ndims.idxmax()].value
+    typ = biggest._constructor
+    axes = biggest.axes
+    naxes = len(axes)
+
+    for term in (terms[i] for i in term_index):
+        for axis, items in enumerate(term.value.axes):
+            if com.is_series(term.value) and naxes > 1:
+                ax, itm = naxes - 1, term.value.index
+            else:
+                ax, itm = axis, items
+            axes[ax] = axes[ax].join(itm, how='outer')
+
+    for i, ndim in ndims.iteritems():
+        for axis, items in izip(xrange(ndim), axes):
+            ti = terms[i].value
+
+            if hasattr(ti, 'reindex_axis'):
+                transpose = com.is_series(ti) and naxes > 1
+
+                if transpose:
+                    f = partial(ti.reindex, index=axes[naxes - 1], copy=False)
+                else:
+                    f = partial(ti.reindex_axis, items, axis=axis, copy=False)
+
+                if pd.lib.is_bool_array(ti.values):
+                    r = f(fill_value=True)
+                else:
+                    r = f()
+
+                terms[i].update(r)
+
+        res = _maybe_promote_shape(terms[i].value.T if transpose else
+                                   terms[i].value, naxes)
+        res = res.T if transpose else res
+
+        try:
+            v = res.values
+        except AttributeError:
+            v = res
+        terms[i].update(v)
+
+    return typ, _zip_axes_from_type(typ, axes)
+
+
+def _filter_terms(flat):
+    # numeric literals
+    literals = set(filter(is_const, flat))
+
+    # these are strings which are variable names
+    names = set(flat) - literals
+
+    # literals are not names and names are not literals, so intersection should
+    # be empty
+    if literals & names:
+        raise ValueError('literals cannot be names and names cannot be '
+                         'literals')
+    return names, literals
+
+
+def _align(terms, env):
+    # flatten the parse tree (a nested list)
+    terms = list(flatten(terms))
+
+    # separate names and literals
+    names, literals = _filter_terms(terms)
+
+    if not names:  # only literals so just promote to a common type
+        return np.result_type(*literals).type, None
+
+    # if all resolved variables are numeric scalars
+    if all(term.isscalar for term in terms):
+        return np.result_type(*(term.value for term in terms)).type, None
+
+    # perform the main alignment
+    typ, axes = _align_core(terms)
+    return typ, axes
+
+
+def _reconstruct_object(typ, obj, axes):
+    """Reconstruct an object given its type, raw value, and possibly empty
+    (None) axes.
+
+    Parameters
+    ----------
+    typ : object
+        A type
+    obj : object
+        The value to use in the type constructor
+    axes : dict
+        The axes to use to construct the resulting pandas object
+
+    Returns
+    -------
+    reconst : typ
+        An object of type ``typ`` with the value `obj` and possible axes
+        `axes`.
+    """
+    try:
+        # handle numpy dtypes
+        typ = typ.type
+    except AttributeError:
+        pass
+
+    if (not isinstance(typ, partial) and
+        issubclass(typ, pd.core.generic.PandasObject)):
+        return typ(obj, **axes)
+
+    ret_value = typ(obj)
+
+    try:
+        return ret_value.item()
+    except (AttributeError, ValueError):
+        return ret_value
+

pandas/computation/api.py

@@ -0,0 +1,2 @@
+from pandas.computation.eval import eval
+from pandas.computation.expr import Expr

pandas/computation/common.py

@@ -0,0 +1,11 @@
+import collections
+from pandas.core.common import is_string
+
+
+def flatten(l):
+    for el in l:
+        if isinstance(el, collections.Iterable) and not is_string(el):
+            for s in flatten(el):
+                yield s
+        else:
+            yield el

pandas/computation/engines.py

@@ -0,0 +1,78 @@
+import abc
+
+from pandas.computation.align import _align, _reconstruct_object
+
+
+class AbstractEngine(object):
+    """"""
+    __metaclass__ = abc.ABCMeta
+
+    has_neg_frac = False
+
+    def __init__(self, expr):
+        self.expr = expr
+        self.aligned_axes = None
+        self.result_type = None
+
+    @abc.abstractmethod
+    def convert(self):
+        """Convert an expression for evaluation."""
+        pass
+
+    def evaluate(self):
+        if not self._is_aligned:
+            self.result_type, self.aligned_axes = _align(self.expr.terms,
+                                                         self.expr.env)
+
+        res = self._evaluate(self.expr.env)
+        return _reconstruct_object(self.result_type, res, self.aligned_axes)
+
+    @property
+    def _is_aligned(self):
+        return self.aligned_axes is not None and self.result_type is not None
+
+    @abc.abstractmethod
+    def _evaluate(self, env):
+        """Return an evaluated expression."""
+        pass
+
+
+class NumExprEngine(AbstractEngine):
+    """NumExpr engine class"""
+    has_neg_frac = True
+
+    def __init__(self, expr):
+        super(NumExprEngine, self).__init__(expr)
+
+    def convert(self):
+        """Return a string"""
+        return '%s' % self.expr
+
+    def _evaluate(self, env):
+        import numexpr as ne
+
+        try:
+            return ne.evaluate(self.convert(), local_dict=env.locals,
+                               global_dict=env.globals,
+                               truediv=self.expr.truediv)
+        except KeyError as e:
+            raise NameError('{0!r} is not defined'.format(e.message))
+
+
+class PythonEngine(AbstractEngine):
+    """Use NumPy even if numexpr is installed"""
+    has_neg_frac = False
+
+    def __init__(self, expr):
+        super(PythonEngine, self).__init__(expr)
+
+    def convert(self):
+        pass
+
+    def evaluate(self):
+        return self.expr(self.expr.env)
+
+    def _evaluate(self, env):
+        pass
+
+_engines = {'numexpr': NumExprEngine, 'python': PythonEngine }