Fixes on the code style based on the Code review and flake8.

And Refactored quick_sort method to improve code readability

Author: WadieBishoy25

audio_filters/butterworth_filter.py

@@ -5,8 +5,10 @@
 """
 Create 2nd-order IIR filters with Butterworth design.
 
-Code based on https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html
-Alternatively you can use scipy.signal.butter, which should yield the same results.
+Code based on
+https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html
+Alternatively you can use scipy.signal.butter,
+ which should yield the same results.
 """
 
 
@@ -20,8 +22,8 @@ def make_lowpass(
 
     >>> filter = make_lowpass(1000, 48000)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.004277569313094809,
-     0.008555138626189618, 0.004277569313094809]
+    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427,
+    0.004277569313094809,0.008555138626189618, 0.004277569313094809]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
@@ -50,8 +52,8 @@ def make_highpass(
 
     >>> filter = make_highpass(1000, 48000)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.9957224306869052,
-     -1.9914448613738105, 0.9957224306869052]
+    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427,
+      0.9957224306869052,-1.9914448613738105, 0.9957224306869052]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
@@ -80,8 +82,8 @@ def make_bandpass(
 
     >>> filter = make_bandpass(1000, 48000)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.06526309611002579,
-     0, -0.06526309611002579]
+    [1.0922959556412573, -1.9828897227476208,
+      0.9077040443587427, 0.06526309611002579,0, -0.06526309611002579]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
@@ -111,8 +113,8 @@ def make_allpass(
 
     >>> filter = make_allpass(1000, 48000)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 0.9077040443587427,
-     -1.9828897227476208, 1.0922959556412573]
+    [1.0922959556412573, -1.9828897227476208, 0.9077040443587427, 
+    0.9077040443587427, -1.9828897227476208, 1.0922959556412573]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
@@ -139,8 +141,8 @@ def make_peak(
 
     >>> filter = make_peak(1000, 48000, 6)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [1.0653405327119334, -1.9828897227476208, 0.9346594672880666, 1.1303715025601122,
-     -1.9828897227476208, 0.8696284974398878]
+    [1.0653405327119334, -1.9828897227476208, 0.9346594672880666,
+      1.1303715025601122,-1.9828897227476208, 0.8696284974398878]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
@@ -171,8 +173,8 @@ def make_lowshelf(
 
     >>> filter = make_lowshelf(1000, 48000, 6)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [3.0409336710888786, -5.608870992220748, 2.602157875636628, 3.139954022810743,
-     -5.591841778072785, 2.5201667380627257]
+    [3.0409336710888786, -5.608870992220748, 2.602157875636628, 
+    3.139954022810743, -5.591841778072785, 2.5201667380627257]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)
@@ -208,8 +210,8 @@ def make_highshelf(
 
     >>> filter = make_highshelf(1000, 48000, 6)
     >>> filter.a_coeffs + filter.b_coeffs  # doctest: +NORMALIZE_WHITESPACE
-    [2.2229172136088806, -3.9587208137297303, 1.7841414181566304, 4.295432981120543,
-     -7.922740859457287, 3.6756456963725253]
+    [2.2229172136088806, -3.9587208137297303, 1.7841414181566304, 
+    4.295432981120543, -7.922740859457287, 3.6756456963725253]
     """
     w0 = tau * frequency / samplerate
     _sin = sin(w0)