update

Task/Prime-decomposition/Python/prime-decomposition-2.py

@@ -1,18 +1,21 @@
-primelist = [2,3]
+primelist = [2, 3]
 def is_prime(n):
-	for y in primes():
-		if not n % y: return False
-		if n > y * y: return True
+    if n in primelist: return True
+    if n < primelist[-1]: return False
+
+    for y in primes():
+        if not n % y: return False
+        if n < y * y: return True
 
 def primes():
-	for n in primelist: yield n
+    for n in primelist: yield n
 
-	n = primelist[-1] + 2
-	while True:
-		n += 2
-		for x in primelist:
-			if not n % x: break
-			if x * x > n:
-				primelist.append(n)
-				yield n
-				break
+    n = primelist[-1]
+    while True:
+        n += 2
+        for x in primelist:
+            if not n % x: break
+            if x * x > n:
+                primelist.append(n)
+                yield n
+                break