diff --git a/docs/development/custom-vectors/arc4/generate_arc4.py b/docs/development/custom-vectors/arc4/generate_arc4.py
index 093bb49..3dee44a 100644
--- a/docs/development/custom-vectors/arc4/generate_arc4.py
+++ b/docs/development/custom-vectors/arc4/generate_arc4.py
@@ -12,8 +12,10 @@
 
 
 _RFC6229_KEY_MATERIALS = [
-    (True, 8*'0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20'),
-    (False, 8*'1ada31d5cf688221c109163908ebe51debb46227c6cc8b37641910833222772a')
+    (True,
+     8 * '0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20'),
+    (False,
+     8 * '1ada31d5cf688221c109163908ebe51debb46227c6cc8b37641910833222772a')
 ]
 
 
@@ -47,25 +49,30 @@
 def _key_for_size(size, keyinfo):
     msb, key = keyinfo
     if msb:
-        return key[:size//4]
+        return key[:size // 4]
     else:
-        return key[-size//4:]
+        return key[-size // 4:]
 
 
 def _build_vectors():
     count = 0
     output = []
     key = None
-    plaintext = binascii.unhexlify(32*'0')
+    plaintext = binascii.unhexlify(32 * '0')
     for size in _SIZES_TO_GENERATE:
         for keyinfo in _RFC6229_KEY_MATERIALS:
             key = _key_for_size(size, keyinfo)
-            cipher = ciphers.Cipher(algorithms.ARC4(binascii.unhexlify(key)), None, default_backend())
+            cipher = ciphers.Cipher(
+                algorithms.ARC4(binascii.unhexlify(key)),
+                None,
+                default_backend())
             encryptor = cipher.encryptor()
             current_offset = 0
             for offset in _RFC6229_OFFSETS:
                 if offset % 16 != 0:
-                    raise ValueError("Offset {} is not evenly divisible by 16".format(offset))
+                    raise ValueError(
+                        "Offset {} is not evenly divisible by 16"
+                        .format(offset))
                 while current_offset < offset:
                     encryptor.update(plaintext)
                     current_offset += len(plaintext)
@@ -73,8 +80,10 @@
                 count += 1
                 output.append("KEY = {}".format(key))
                 output.append("OFFSET = {}".format(offset))
-                output.append("PLAINTEXT = {}".format(binascii.hexlify(plaintext)))
-                output.append("CIPHERTEXT = {}".format(binascii.hexlify(encryptor.update(plaintext))))
+                output.append("PLAINTEXT = {}".format(
+                    binascii.hexlify(plaintext)))
+                output.append("CIPHERTEXT = {}".format(
+                    binascii.hexlify(encryptor.update(plaintext))))
                 current_offset += len(plaintext)
             assert not encryptor.finalize()
     return "\n".join(output)