Add timing column conversion and MidiPiece

addition

fortepyan/midi/structures.py

@@ -1,3 +1,4 @@
+from warnings import showwarning
 from dataclasses import field, dataclass
 
 import numpy as np
@@ -31,6 +32,10 @@ def __post_init__(self):
         elif "duration" not in self.df.columns:
             self.df["duration"] = self.df["end"] - self.df["start"]
 
+        # Convert timing columns to float to ensure consistency
+        for col in timing_columns:
+            self.df[col] = self.df[col].astype(float)
+
         # Check for the absolutely required columns: 'pitch' and 'velocity'
         if "pitch" not in self.df.columns:
             raise ValueError("The DataFrame is missing the required column: 'pitch'.")
@@ -109,6 +114,35 @@ def __getitem__(self, index: slice) -> "MidiPiece":
 
         return out
 
+    def __add__(self, other: "MidiPiece") -> "MidiPiece":
+        if not isinstance(other, MidiPiece):
+            raise TypeError("You can only add MidiPiece objects to other MidiPiece objects.")
+
+        # Adjust the start/end times of the second piece
+        other.df.start += self.end
+        other.df.end += self.end
+
+        # Concatenate the two pieces
+        df = pd.concat([self.df, other.df], ignore_index=True)
+
+        # make sure the other piece is not modified
+        other.df.start -= self.end
+        other.df.end -= self.end
+
+        # make sure that start and end times are floats
+        df.start = df.start.astype(float)
+        df.end = df.end.astype(float)
+
+        out = MidiPiece(df=df)
+
+        # Show warning as the piece might not be musically valid.
+        showwarning("The resulting piece may not be musically valid.", UserWarning, "fortepyan", lineno=1)
+
+        return out
+
+    def __len__(self) -> int:
+        return self.size
+
     @property
     def duration(self) -> float:
         duration = self.df.end.max() - self.df.start.min()

tests/midi/test_structures.py

@@ -9,7 +9,7 @@
 def sample_df():
     df = pd.DataFrame(
         {
-            "start": [0, 1, 2, 3, 4],
+            "start": [0.0, 1, 2, 3, 4],
             "end": [1, 2, 3, 4, 5.5],
             "duration": [1, 1, 1, 1, 1.5],
             "pitch": [60, 62, 64, 65, 67],
@@ -114,3 +114,57 @@ def test_to_midi(sample_midi_piece):
     midi_end_time = midi_track.get_end_time()
 
     assert midi_end_time == expected_end_time, f"MIDI end time {midi_end_time} does not match expected {expected_end_time}"
+
+
+def test_add_two_midi_pieces(sample_midi_piece):
+    # Create a second MidiPiece to add to the sample one
+    df2 = pd.DataFrame(
+        {
+            "start": [0, 1, 2],
+            "end": [1, 2, 3],
+            "duration": [1, 1, 1],
+            "pitch": [70, 72, 74],
+            "velocity": [80, 80, 80],
+        }
+    )
+    midi_piece2 = MidiPiece(df=df2)
+
+    # Add the two pieces together
+    combined_piece = sample_midi_piece + midi_piece2
+
+    # Check that the resulting piece has the correct number of notes
+    assert len(combined_piece) == len(sample_midi_piece) + len(midi_piece2)
+
+    # Check if duration has been adjusted
+    assert combined_piece.duration == sample_midi_piece.duration + midi_piece2.duration
+
+
+def test_add_non_midi_piece(sample_midi_piece):
+    # Try to add a non-MidiPiece object to a MidiPiece
+    with pytest.raises(TypeError):
+        _ = sample_midi_piece + "not a MidiPiece"
+
+
+def test_add_does_not_modify_originals(sample_midi_piece):
+    # Create a second MidiPiece to add to the sample one
+    df2 = pd.DataFrame(
+        {
+            "start": [0, 1, 2],
+            "end": [1, 2, 3],
+            "duration": [1, 1, 1],
+            "pitch": [70, 72, 74],
+            "velocity": [80, 80, 80],
+        }
+    )
+    midi_piece2 = MidiPiece(df=df2)
+
+    # Store the original dataframes for comparison
+    original_df1 = sample_midi_piece.df.copy()
+    original_df2 = midi_piece2.df.copy()
+
+    # Add the two pieces together
+    _ = sample_midi_piece + midi_piece2
+
+    # Check that the original pieces have not been modified
+    pd.testing.assert_frame_equal(sample_midi_piece.df, original_df1)
+    pd.testing.assert_frame_equal(midi_piece2.df, original_df2)