fixes petl-developers#339 by adding biselect

docs/transform.rst

@@ -85,6 +85,7 @@ Selecting rows
 .. autofunction:: petl.transform.selects.selectusingcontext
 .. autofunction:: petl.transform.selects.rowlenselect
 .. autofunction:: petl.transform.selects.facet
+.. autofunction:: petl.transform.selects.biselect
 
 
 .. _transform_regex:

petl/transform/__init__.py

@@ -13,11 +13,12 @@
 
 from petl.transform.sorts import sort, mergesort, issorted
 
-from petl.transform.selects import select, selectop, selectcontains, selecteq, \
-    selectfalse, selectge, selectgt, selectin, selectis, selectisinstance, \
-    selectisnot, selectle, selectlt, selectne, selectnone, selectnotin, \
-    selectnotnone, selectrangeclosed, selectrangeopen, selectrangeopenleft, \
-    selectrangeopenright, selecttrue, selectusingcontext, rowlenselect, facet
+from petl.transform.selects import select, selectop, selectcontains, \
+    selecteq, selectfalse, selectge, selectgt, selectin, selectis, \
+    selectisinstance, selectisnot, selectle, selectlt, selectne, selectnone, \
+    selectnotin, selectnotnone, selectrangeclosed, selectrangeopen, \
+    selectrangeopenleft, selectrangeopenright, selecttrue, \
+    selectusingcontext, rowlenselect, facet, biselect
 
 from petl.transform.joins import join, leftjoin, rightjoin, outerjoin, \
     crossjoin, antijoin, lookupjoin, unjoin

petl/transform/selects.py

@@ -481,3 +481,52 @@ def facet(table, key):
 
 
 Table.facet = facet
+
+
+def biselect(table, *args, **kwargs):
+    """Return two tables, the first containing selected rows, the second
+    containing remaining rows. E.g.::
+
+        >>> import petl as etl
+        >>> table1 = [['foo', 'bar', 'baz'],
+        ...           ['a', 4, 9.3],
+        ...           ['a', 2, 88.2],
+        ...           ['b', 1, 23.3],
+        ...           ['c', 8, 42.0],
+        ...           ['d', 7, 100.9],
+        ...           ['c', 2]]
+        >>> table2, table3 = etl.biselect(table1, lambda rec: rec.foo == 'a')
+        >>> table2
+        +-----+-----+------+
+        | foo | bar | baz  |
+        +=====+=====+======+
+        | 'a' |   4 |  9.3 |
+        +-----+-----+------+
+        | 'a' |   2 | 88.2 |
+        +-----+-----+------+
+        >>> table3
+        +-----+-----+-------+
+        | foo | bar | baz   |
+        +=====+=====+=======+
+        | 'b' |   1 |  23.3 |
+        +-----+-----+-------+
+        | 'c' |   8 |  42.0 |
+        +-----+-----+-------+
+        | 'd' |   7 | 100.9 |
+        +-----+-----+-------+
+        | 'c' |   2 |       |
+        +-----+-----+-------+
+
+    .. versionadded:: 1.1.0
+
+    """
+
+    # override complement kwarg
+    kwargs['complement'] = False
+    t1 = select(table, *args, **kwargs)
+    kwargs['complement'] = True
+    t2 = select(table, *args, **kwargs)
+    return t1, t2
+
+
+Table.biselect = biselect