added random binary

CHANGELOG.md

 # v2.14.34
 
 * added iterate_callable
+* added random_binary
+

docs/random.rst

@@ -6,3 +6,8 @@ shuffle_together
 ----------------
 
 .. autofunction:: satella.random.shuffle_together
+
+random_binary
+-------------
+
+.. autofunction:: satella.random.random_binary

satella/random.py

+import os
 import random
 import typing as tp
 
-__all__ = ['shuffle_together']
+__all__ = ['shuffle_together', 'random_binary']
+
+
+def random_binary(length: int) -> bytes:
+    """
+    Return a random bytes string of given length.
+
+    An attempt will be made to utilize /dev/random, if exists
+
+    :param length: length of string to generate
+    """
+    if os.path.exists('/dev/random'):
+        with open('/dev/random', 'rb') as f_in:
+            return f_in.read(length)
+    else:
+        return bytes([random.randint(0, 255) for _ in range(length)])
 
 
 def shuffle_together(*args: tp.Sequence) -> tp.List[tp.List]:

tests/test_random.py

 import unittest
-from satella.random import shuffle_together
+from satella.random import shuffle_together, random_binary
 
 
 class TestRandom(unittest.TestCase):
+    def test_random_binary(self):
+        self.assertFalse(random_binary(0))
+        self.assertEqual(len(random_binary(10)), 10)
+
     def test_random(self):
         a = [(1, 2, 3), ('a', 'b', 'c')]
         b = zip(*shuffle_together(*a))