fix: address review findings for nominal frequency labels

- Fix lint: remove unused pytest import, rename ambiguous 'l' → 'label' (E741)
- Fix __init__.py overloads: add Literal[True] nominal variants returning List[str]
- Fix duplicate label computation: reuse getansifrequencies labels via slice
- Add docstring to _nominal_freq_for_band explaining fallback behavior
- Fix mypy: annotate extended list, add type: ignore for overload dispatch
- Add trailing newline to __init__.py

Author: jmrplens

src/pyoctaveband/__init__.py

@@ -52,7 +52,7 @@ def octavefilter(
     calibration_factor: float = 1.0,
     dbfs: bool = False,
     mode: str = "rms",
-    nominal: bool = False,
+    nominal: Literal[False] = False,
 ) -> Tuple[np.ndarray, List[float]]: ...
 
 
@@ -73,10 +73,52 @@ def octavefilter(
     calibration_factor: float = 1.0,
     dbfs: bool = False,
     mode: str = "rms",
-    nominal: bool = False,
+    nominal: Literal[False] = False,
 ) -> Tuple[np.ndarray, List[float], List[np.ndarray]]: ...
 
 
+@overload
+def octavefilter(
+    x: List[float] | np.ndarray,
+    fs: int,
+    fraction: float = 1,
+    order: int = 6,
+    limits: List[float] | None = None,
+    show: bool = False,
+    sigbands: Literal[False] = False,
+    plot_file: str | None = None,
+    detrend: bool = True,
+    filter_type: str = "butter",
+    ripple: float = 0.1,
+    attenuation: float = 60.0,
+    calibration_factor: float = 1.0,
+    dbfs: bool = False,
+    mode: str = "rms",
+    nominal: Literal[True] = ...,
+) -> Tuple[np.ndarray, List[str]]: ...
+
+
+@overload
+def octavefilter(
+    x: List[float] | np.ndarray,
+    fs: int,
+    fraction: float = 1,
+    order: int = 6,
+    limits: List[float] | None = None,
+    show: bool = False,
+    sigbands: Literal[True] = True,
+    plot_file: str | None = None,
+    detrend: bool = True,
+    filter_type: str = "butter",
+    ripple: float = 0.1,
+    attenuation: float = 60.0,
+    calibration_factor: float = 1.0,
+    dbfs: bool = False,
+    mode: str = "rms",
+    nominal: Literal[True] = ...,
+) -> Tuple[np.ndarray, List[str], List[np.ndarray]]: ...
+
+
 def octavefilter(
     x: List[float] | np.ndarray,
     fs: int,
@@ -149,6 +191,6 @@ def octavefilter(
     )
 
     if sigbands:
-        return filter_bank.filter(x, sigbands=True, mode=mode, detrend=detrend, nominal=nominal)
+        return filter_bank.filter(x, sigbands=True, mode=mode, detrend=detrend, nominal=nominal)  # type: ignore[call-overload,no-any-return]
     else:
-        return filter_bank.filter(x, sigbands=False, mode=mode, detrend=detrend, nominal=nominal)
+        return filter_bank.filter(x, sigbands=False, mode=mode, detrend=detrend, nominal=nominal)  # type: ignore[call-overload,no-any-return]

src/pyoctaveband/frequencies.py

@@ -121,9 +121,10 @@ def _genfreqs(
     :param fs: Sample rate.
     :return: Tuple of center, lower, upper frequencies, and nominal labels.
     """
-    freq, freq_d, freq_u, _ = getansifrequencies(fraction, limits)
+    freq, freq_d, freq_u, labels = getansifrequencies(fraction, limits)
     freq, freq_d, freq_u = _deleteouters(freq, freq_d, freq_u, fs)
-    labels = [_format_nominal_freq(_nominal_freq_for_band(f, fraction)) for f in freq]
+    # _deleteouters only removes trailing bands above Nyquist, so slice labels
+    labels = labels[: len(freq)]
     return freq, freq_d, freq_u, labels
 
 
@@ -138,11 +139,16 @@ def _iec_e3_round(f: float) -> float:
 
 
 def _nominal_freq_for_band(exact_freq: float, fraction: float) -> float:
-    """Return IEC 61260-1 nominal frequency (float) for an exact mid-band frequency."""
+    """Return IEC 61260-1 nominal frequency (float) for an exact mid-band frequency.
+
+    For standard fractions (1, 3), snaps to the IEC preferred table via
+    ``normalizedfreq``.  For non-standard fractions, falls back to Annex E.3
+    significant-figure rounding (``_iec_e3_round``).
+    """
     frac = round(fraction)
     if frac in (1, 3):
         base = normalizedfreq(frac)
-        extended = [f * (10 ** d) for d in range(-3, 4) for f in base]
+        extended: List[float] = [f * (10 ** d) for d in range(-3, 4) for f in base]
         return min(extended, key=lambda f: abs(np.log(f / exact_freq)))
     return _iec_e3_round(exact_freq)
 

tests/test_nominal_frequencies.py

@@ -4,7 +4,6 @@
 """
 
 import numpy as np
-import pytest
 
 from pyoctaveband.frequencies import (
     _format_nominal_freq,
@@ -66,7 +65,7 @@ def test_format_1k_and_above():
 def test_getansifrequencies_returns_labels():
     freq, fd, fu, labels = getansifrequencies(fraction=3)
     assert isinstance(labels, list)
-    assert all(isinstance(l, str) for l in labels)
+    assert all(isinstance(label, str) for label in labels)
     assert len(labels) == len(freq)
     assert "1k" in labels
     assert "31.5" in labels
@@ -84,7 +83,7 @@ def test_filterbank_nominal_freq_attribute():
     fb = OctaveFilterBank(fs=48000, fraction=1)
     assert hasattr(fb, "nominal_freq")
     assert isinstance(fb.nominal_freq, list)
-    assert all(isinstance(l, str) for l in fb.nominal_freq)
+    assert all(isinstance(label, str) for label in fb.nominal_freq)
     assert "1k" in fb.nominal_freq
     assert len(fb.nominal_freq) == fb.num_bands