Using set instead of list, it's faster.

sybrenstuvel · sybrenstuvel · commit c28cb8951203 · 2016-03-17T16:20:12.000+01:00
diff --git a/rsa/prime.py b/rsa/prime.py
@@ -103,7 +103,7 @@ def is_prime(number):
 
     # Check for small numbers.
     if number < 10:
-        return number in [2, 3, 5, 7]
+        return number in {2, 3, 5, 7}
 
     # Check for even numbers.
     if not (number & 1):
