[pull] master from biopython:master

Bio/Align/__init__.py

@@ -3723,7 +3723,7 @@ def substitutions(self):
                     start1, start2 = end1, end2
         return m
 
-    def counts(self, substitution_matrix=None, gaps_only=False):
+    def counts(self, substitution_matrix=None, ignore_sequences=False):
         """Count the number of identities, mismatches, and gaps of an alignment.
 
         Arguments:
@@ -3733,12 +3733,13 @@ def counts(self, substitution_matrix=None, gaps_only=False):
                                  (typically from the ``Bio.Align.substitution_matrices``
                                  submodule) to also calculate the number of positive
                                  matches in an amino acid alignment.
-         - gaps_only           - If True, do not calculate the number of identities,
+         - ignore_sequences    - If True, do not calculate the number of identities,
                                  positives, and mismatches, but only calculate the
-                                 number of gaps. This will speed up the calculation.
+                                 number of aligned sequences and number of gaps
+                                 to speed up the calculation.
                                  Default value: False.
 
-        A ValueError is raised if gaps_only is True and substitution_matrix is not None.
+        A ValueError is raised if ignore_sequences is True and substitution_matrix is not None.
 
         >>> aligner = PairwiseAligner(mode='global', match_score=2, mismatch_score=-1)
         >>> for alignment in aligner.align("TACCG", "ACG"):
@@ -3793,16 +3794,18 @@ def counts(self, substitution_matrix=None, gaps_only=False):
         right_insertions = right_deletions = 0
         internal_insertions = internal_deletions = 0
         aligned = 0
-        if gaps_only:
+        if ignore_sequences:
             identities = None
             mismatches = None
         else:
             identities = 0
             mismatches = 0
         if substitution_matrix is None:
             positives = None
-        elif gaps_only:
-            raise ValueError("gaps_only cannot be True if substitution_matrix is used")
+        elif ignore_sequences:
+            raise ValueError(
+                "ignore_sequences cannot be True if substitution_matrix is used"
+            )
         else:
             positives = 0
         sequences = [None] * len(self.sequences)
@@ -3813,7 +3816,7 @@ def counts(self, substitution_matrix=None, gaps_only=False):
         for i, sequence in enumerate(self.sequences):
             start = min(coordinates[i, :])
             end = max(coordinates[i, :])
-            if not gaps_only:
+            if not ignore_sequences:
                 try:
                     sequence = sequence[start:end]
                 except ValueError:
@@ -3823,10 +3826,10 @@ def counts(self, substitution_matrix=None, gaps_only=False):
             if sum(aligned_steps > 0) > sum(aligned_steps < 0):
                 coordinates[i, :] = coordinates[i, :] - start
             else:
-                if not gaps_only:
+                if not ignore_sequences:
                     sequence = reverse_complement(sequence)
                 coordinates[i, :] = end - coordinates[i, :]
-            if gaps_only:
+            if ignore_sequences:
                 sequences[i] = None
             else:
                 try:

Doc/Tutorial/chapter_align.rst

@@ -581,9 +581,10 @@ alignment are indicated by -1:
 Counting identities, mismatches, and gaps
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The ``counts`` method counts the number of identities, mismatches, and gaps
-(insertions and deletions) of an alignment.  The return value is an
-``AlignmentCounts`` object, from which the counts can be obtained as properties.
+The ``counts`` method counts the number of identities, mismatches, aligned
+letters, and agaps (insertions and deletions) of an alignment.  The return
+value is an ``AlignmentCounts`` object, from which the counts can be obtained
+as properties.
 
 .. cont-doctest
 
@@ -656,6 +657,26 @@ number of gaps (= insertions + deletions):
    >>> counts.internal_gaps
    2
 
+To speed up the calculation, you can use ``ignore_sequences=True`` to skip
+counting the number of matches and mismatches (this will still calculate the
+number of aligned sequences):
+
+.. cont-doctest
+
+.. code:: pycon
+
+   >>> counts = alignment.counts(ignore_sequences=True)
+   >>> counts.aligned
+   16
+   >>> print(counts.identities)
+   None
+   >>> print(counts.mismatches)
+   None
+   >>> counts.insertions
+   1
+   >>> counts.deletions
+   5
+
 For protein alignments, in addition to the number of identities and mismatches,
 you can also count the number of positive matches by supplying a substitution
 matrix (see Chapter :ref:`sec:substitution_matrices`):

Tests/test_Align_Alignment.py

@@ -2376,13 +2376,15 @@ def test_counts(self):
             str(counts),
             "AlignmentCounts(left_insertions=0, left_deletions=0, internal_insertions=0, internal_deletions=0, right_insertions=80, right_deletions=4, aligned=3084, identities=3020, mismatches=64, positives=None)",
         )
-        counts = alignment.counts(gaps_only=True)
+        counts = alignment.counts(ignore_sequences=True)
         self.assertEqual(
             str(counts),
             "AlignmentCounts(left_insertions=0, left_deletions=0, internal_insertions=0, internal_deletions=0, right_insertions=80, right_deletions=4, aligned=3084, identities=None, mismatches=None, positives=None)",
         )
         with self.assertRaises(ValueError):
-            alignment.counts(substitution_matrix=substitution_matrix, gaps_only=True)
+            alignment.counts(
+                substitution_matrix=substitution_matrix, ignore_sequences=True
+            )
         for i, sequence in enumerate(alignment.sequences):
             length = len(sequence)
             alignment.sequences[i] = Seq(None, length)