Add utility for removing duplicated objects (e.g. keys, clefs)

music21/stream/__init__.py

@@ -24,3 +24,4 @@
 from music21.stream import iterator
 from music21.stream import makeNotation
 from music21.stream import streamStatus
+from music21.stream import tools

music21/stream/tools.py

@@ -0,0 +1,188 @@
+# -*- coding: utf-8 -*-
+# ------------------------------------------------------------------------------
+# Name:         stream/tools.py
+# Purpose:      Additional tools for working with streams
+#
+# Authors:      Mark Gotham
+#
+# Copyright:    Copyright © 2022 Michael Scott Asato Cuthbert
+# License:      BSD, see license.txt
+# ------------------------------------------------------------------------------
+
+from __future__ import annotations
+
+from music21 import clef
+from music21 import environment
+from music21 import key
+from music21 import meter
+from music21 import stream
+
+from copy import deepcopy
+
+environLocal = environment.Environment('stream.tools')
+
+
+# ------------------------------------------------------------------------------
+
+def removeDuplicates(thisStream: stream.Stream,
+                     classesToRemove: list = [meter.TimeSignature, key.KeySignature, clef.Clef],
+                     inPlace: bool = True
+                     ) -> stream.Stream:
+    '''
+    The repetition of some classes like notes is common.
+    By contrast, the explicit repetition of certain other objects like clefs
+    usually indicates an error e.g., resulting from a copy'n'paste.
+    This function serves to remove those that are likely in error and make no change.
+
+    Use the `classesToRemove` argument to specify which music21 classes to check and remove.
+    The classes currently supported are: time signatures, key signatures, and clefs.
+    The `classesToRemove` arument defaults all three.
+    Sometimes there are legitimate reasons to duplicate even these classes.
+    In that case, override the default by specifying the list of which of the three of classes.
+    More classes may be added, but for now they will simply raise a ValueError.
+
+    So let's create an example part with an initial set of
+    time signature, key signature, and clef.
+
+    >>> s = stream.Part()
+    >>> s.append(meter.TimeSignature('3/4'))  # first TS
+    >>> s.append(key.KeySignature(6))  # first KS
+    >>> s.append(clef.TrebleClef())  # first Clef
+
+    Then a few notes, followed by a duplicates of the
+    key signature, and clef.
+
+    >>> s.append(note.Note('C'))
+    >>> s.append(note.Note('C'))
+    >>> s.append(note.Note('D'))
+
+    >>> s.append(meter.TimeSignature('3/4'))  # duplicate
+    >>> s.append(key.KeySignature(6))  # duplicate
+    >>> s.append(clef.TrebleClef())  # duplicate
+
+    Finally, a few more notes, followed by a
+    change of time signature, key signature, and clef.
+
+    >>> s.append(note.Note('E'))
+    >>> s.append(note.Note('F'))
+    >>> s.append(note.Note('G'))
+
+    >>> s.append(meter.TimeSignature('2/4'))
+    >>> s.append(key.KeySignature(-5))
+    >>> s.append(clef.BassClef())
+
+    >>> s.append(note.Note('A'))
+    >>> s.append(note.Note('B'))
+    >>> s.append(note.Note('C5'))
+
+    Now we'll make it into a proper part with measures and see
+    how it looks in its original, unaltered form:
+
+    >>> s.makeMeasures(inPlace=True)
+    >>> s.show('t')
+    {0.0} <music21.stream.Measure 1 offset=0.0>
+        {0.0} <music21.clef.TrebleClef>
+        {0.0} <music21.key.KeySignature of 6 sharps>
+        {0.0} <music21.meter.TimeSignature 3/4>
+        {0.0} <music21.note.Note C>
+        {1.0} <music21.note.Note C>
+        {2.0} <music21.note.Note D>
+    {3.0} <music21.stream.Measure 2 offset=3.0>
+        {0.0} <music21.clef.TrebleClef>
+        {0.0} <music21.key.KeySignature of 6 sharps>
+        {0.0} <music21.meter.TimeSignature 3/4>
+        {0.0} <music21.note.Note E>
+        {1.0} <music21.note.Note F>
+        {2.0} <music21.note.Note G>
+    {6.0} <music21.stream.Measure 3 offset=6.0>
+        {0.0} <music21.clef.BassClef>
+        {0.0} <music21.key.KeySignature of 5 flats>
+        {0.0} <music21.meter.TimeSignature 2/4>
+        {0.0} <music21.note.Note A>
+        {1.0} <music21.note.Note B>
+    {8.0} <music21.stream.Measure 4 offset=8.0>
+        {0.0} <music21.note.Note C>
+        {1.0} <music21.bar.Barline type=final>
+
+    Calling removeDuplicates should remove the duplicates
+    even with those changes now stored within measures,
+    not directly on the part.
+    Specifically, in our example,
+    the duplicates entries are removed from measure 2
+    and the actual changes in measure 3 remain.
+
+    >>> testInPlace = stream.tools.removeDuplicates(s)
+    >>> testInPlace.show('t')
+    {0.0} <music21.stream.Measure 1 offset=0.0>
+        {0.0} <music21.clef.TrebleClef>
+        {0.0} <music21.key.KeySignature of 6 sharps>
+        {0.0} <music21.meter.TimeSignature 3/4>
+        {0.0} <music21.note.Note C>
+        {1.0} <music21.note.Note C>
+        {2.0} <music21.note.Note D>
+    {3.0} <music21.stream.Measure 2 offset=3.0>
+        {0.0} <music21.note.Note E>
+        {1.0} <music21.note.Note F>
+        {2.0} <music21.note.Note G>
+    {6.0} <music21.stream.Measure 3 offset=6.0>
+        {0.0} <music21.clef.BassClef>
+        {0.0} <music21.key.KeySignature of 5 flats>
+        {0.0} <music21.meter.TimeSignature 2/4>
+        {0.0} <music21.note.Note A>
+        {1.0} <music21.note.Note B>
+    {8.0} <music21.stream.Measure 4 offset=8.0>
+        {0.0} <music21.note.Note C>
+        {1.0} <music21.bar.Barline type=final>
+
+    As the example shows, this function defaults to working on a stream inPlace.
+
+    >>> testInPlace == s
+    True
+
+    To avoid this, set inPlace to False.
+
+    >>> testNotInPlace = stream.tools.removeDuplicates(s, inPlace=False)
+    >>> testNotInPlace == s
+    False
+
+    '''
+
+    supportedClasses = [meter.TimeSignature, key.KeySignature, clef.Clef]
+
+    removalDict = {}
+
+    if not inPlace:
+        thisStream = deepcopy(thisStream)
+
+    for thisClass in classesToRemove:
+
+        if not any(issubclass(thisClass, supportedClass) for supportedClass in supportedClasses):
+            raise ValueError(f'Invalid class. Only {supportedClasses} are supported.')
+
+        allStates = thisStream.recurse().getElementsByClass(thisClass)
+
+        if len(allStates) < 2:  # Not used, or doesn't change
+            continue
+
+        currentState = allStates[0]  # First to initialize: can't be a duplicate
+        for thisState in allStates[1:]:
+            if thisState == currentState:
+                if thisState.activeSite in removalDict:  # May be several in same (e.g., measure)
+                    removalDict[thisState.activeSite].append(thisState)
+                else:
+                    removalDict[thisState.activeSite] = [thisState]
+            else:
+                currentState = thisState
+
+    for activeSiteKey in removalDict:
+        for x in removalDict[activeSiteKey]:
+            activeSiteKey.remove(x, recurse=True)
+
+    return thisStream
+
+
+# -----------------------------------------------------------------------------
+
+if __name__ == '__main__':
+    import music21
+    music21.mainTest()