Fix sorting of rows with different length using custom itemgetter

docs/changes.rst

@@ -1,6 +1,12 @@
 Changes
 =======
 
+Version 1.7.8
+-------------
+
+* Fix sorting of rows with different length
+  By :user:`arturponinski`, :issue:`385`.
+
 Version 1.7.7
 -------------
 

petl/comparison.py

@@ -2,7 +2,7 @@
 
 
 import operator
-
+from functools import partial
 
 from petl.compat import text_type, binary_type, numeric_types
 
@@ -104,6 +104,26 @@ def _typestr(x):
 
 
 def comparable_itemgetter(*args):
-    f = operator.itemgetter(*args)
+    getter = operator.itemgetter(*args)
+    getter_with_default = _itemgetter_with_default(*args)
+
+    def f(x):
+        try:
+            return getter(x)
+        except (IndexError, KeyError):
+            return getter_with_default(x)
     g = lambda x: Comparable(f(x))
     return g
+
+
+def _itemgetter_with_default(*args):
+    """ itemgetter compatible with `operator.itemgetter` behavior, filling missing
+    values with default instead of raising IndexError or KeyError """
+    def get_default(obj, item, default):
+        try:
+            return obj[item]
+        except (IndexError, KeyError):
+            return default
+    if len(args) == 1:
+        return partial(get_default, item=args[0], default=None)
+    return lambda obj: tuple(get_default(obj, item=item, default=None) for item in args)

petl/test/transform/test_sorts.py

@@ -9,6 +9,7 @@
 
 import pytest
 
+import petl
 from petl.compat import next
 
 
@@ -522,3 +523,21 @@ def test_issorted():
     assert not issorted(table5, key='foo')
     assert issorted(table5, key='foo', reverse=True)
     assert not issorted(table5, key='foo', reverse=True, strict=True)
+
+
+def test_sort_missing_cell_numeric():
+    """ Sorting table with missing values raises IndexError #385 """
+    tbl = (('a', 'b'), ('4',), ('2', '1'), ('1',))
+    expect = (('a', 'b'), ('1',), ('2', '1'), ('4',))
+
+    sorted = sort(tbl)
+    ieq(expect, sorted)
+
+
+def test_sort_missing_cell_text():
+    """ Sorting table with missing values raises IndexError #385 """
+    tbl = (('a', 'b', 'c'), ('C',), ('A', '4', '5'))
+    expect = (('a', 'b', 'c'), ('A', '4', '5'), ('C',))
+
+    sorted = sort(tbl)
+    ieq(expect, sorted)

petl/transform/sorts.py

@@ -295,7 +295,6 @@ def _iternocache(self, source, key, reverse):
         else:
             indices = range(len(hdr))
         # now use field indices to construct a _getkey function
-        # TODO check if this raises an exception on short rows
         getkey = comparable_itemgetter(*indices)
 
         # TODO support native comparison