Luhn's Checksum Algorithm

luhnchecksum.py

@@ -0,0 +1,21 @@
+def luhn_checksum(card_number):
+    def digits_of(n):
+        return [int(d) for d in str(n)]
+
+    digits = digits_of(card_number)
+    odd_digits = digits[-1::-2]
+    even_digits = digits[-2::-2]
+    checksum = 0
+    checksum += sum(odd_digits)
+    for d in even_digits:
+        checksum += sum(digits_of(d * 2))
+    return checksum % 10
+
+
+def is_luhn_valid(card_number):
+    return luhn_checksum(card_number) == 0
+
+
+n = int(input())
+for _ in range(n):
+    print("PASS" if is_luhn_valid(input()) else "FAIL")