Simplify the _rand_exp function

pythonfuzz/corpus.py

@@ -45,18 +45,15 @@ def _rand(n):
             return 0
         return random.randint(0, n-1)
 
-    # Exp2 generates n with probability 1/2^(n+1).
     @staticmethod
     def _rand_exp():
-        rand_bin = bin(random.randint(0, 2**32-1))[2:]
-        rand_bin = '0'*(32 - len(rand_bin)) + rand_bin
-        count = 0
-        for i in rand_bin:
-            if i == '0':
-                count +=1
-            else:
-                break
-        return count
+        """ Return a number `n` between 0 and 32 included,
+            with a probability of 1/2^(n+1)
+        """
+        n = random.getrandbits(32)
+        for i in range(32):
+            if n % (2 << i):
+                return i
 
     @staticmethod
     def _choose_len(n):