Make fft.py conform to PEP8 (#685)

Author: fanninpm

contents/cooley_tukey/code/python/fft.py

@@ -2,56 +2,62 @@
 from cmath import exp, pi
 from math import log2
 
+
 def dft(X):
     N = len(X)
-    temp = [0]*N
+    temp = [0] * N
     for i in range(N):
         for k in range(N):
-            temp[i] += X[k] * exp(-2.0j*pi*i*k/N)
+            temp[i] += X[k] * exp(-2.0j * pi * i * k / N)
     return temp
 
+
 def cooley_tukey(X):
-	N = len(X)
-	if N <= 1:
-		return X
-	even = cooley_tukey(X[0::2])
-	odd =  cooley_tukey(X[1::2])
-
-	temp = [i for i in range(N)]
-	for k in range(N//2):
-		temp[k] = even[k] + exp(-2j*pi*k/N) * odd[k]
-		temp[k+N//2] = even[k] - exp(-2j*pi*k/N)*odd[k]
-	return temp
-
-def bitReverse(X):
-	N = len(X)
-	temp = [i for i in range(N)]
-	for k in range(N):
-		b =  sum(1<<(int(log2(N))-1-i) for i in range(int(log2(N))) if k>>i&1)
-		temp[k] = X[b]
-		temp[b] = X[k]
-	return temp
+    N = len(X)
+    if N <= 1:
+        return X
+    even = cooley_tukey(X[0::2])
+    odd = cooley_tukey(X[1::2])
+
+    temp = [i for i in range(N)]
+    for k in range(N // 2):
+        temp[k] = even[k] + exp(-2.0j * pi * k / N) * odd[k]
+        temp[k + N // 2] = even[k] - exp(-2.0j * pi * k / N) * odd[k]
+    return temp
+
+
+def bit_reverse(X):
+    N = len(X)
+    temp = [i for i in range(N)]
+    for k in range(N):
+        b = sum(1 << int(log2(N)) - 1 -
+                i for i in range(int(log2(N))) if k >> i & 1)
+        temp[k] = X[b]
+        temp[b] = X[k]
+    return temp
+
 
 def iterative_cooley_tukey(X):
-	N = len(X)
+    N = len(X)
+
+    X = bit_reverse(X)
 
-	X = bitReverse(X)
+    for i in range(1, int(log2(N)) + 1):
+        stride = 2 ** i
+        w = exp(-2.0j * pi / stride)
+        for j in range(0, N, stride):
+            v = 1
+            for k in range(stride // 2):
+                X[k + j + stride // 2] = X[k + j] - v * X[k + j + stride // 2]
+                X[k + j] -= X[k + j + stride // 2] - X[k + j]
+                v *= w
+    return X
 
-	for i in range(1, int(log2(N)) + 1):
-		stride = 2**i
-		w = exp(-2j*pi/stride)
-		for j in range(0, N, stride):
-			v = 1
-			for k in range(stride//2):
-				X[k + j + stride//2] = X[k + j] - v*X[k + j + stride//2];
-				X[k + j] -= (X[k + j + stride//2] - X[k + j]);
-				v *= w;
-	return X
 
 X = []
 
 for i in range(64):
-	X.append(random())
+    X.append(random())
 
 Y = cooley_tukey(X)
 Z = iterative_cooley_tukey(X)

contents/cooley_tukey/cooley_tukey.md

@@ -80,7 +80,7 @@ For some reason, though, putting code to this transformation really helped me fi
 {% sample lang="hs" %}
 [import:7-13, lang:"haskell"](code/haskell/fft.hs)
 {% sample lang="py" %}
-[import:5-11, lang:"python"](code/python/fft.py)
+[import:6-12, lang:"python"](code/python/fft.py)
 {% sample lang="scratch" %}
 [import:4-13, lang:"julia"](code/julia/fft.jl)
 {% sample lang="asm-x64" %}
@@ -131,7 +131,7 @@ In the end, the code looks like:
 {% sample lang="hs" %}
 [import:15-28, lang:"haskell"](code/haskell/fft.hs)
 {% sample lang="py" %}
-[import:13-24, lang:"python"](code/python/fft.py)
+[import:15-26, lang:"python"](code/python/fft.py)
 {% sample lang="scratch" %}
 [import:16-32, lang:"julia"](code/julia/fft.jl)
 {% sample lang="asm-x64" %}