Adopted new convention from template

src/Python/Problems001-050/Problem013.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env python
 """
 Created on 1 Jan 2018
 
@@ -20,15 +20,15 @@ def compute():
     Work out the first ten digits of the sum of the following one-hundred
     50-digit numbers.
     """
-    file = Path("../files/Problem13.txt")
-    with open(file, "r") as f:
+    _file = Path("../files/Problem13.txt")
+    with open(_file, "r") as f:
         num = f.readlines()
-        result = 0
+        ans = 0
         for line in num:
-            result += int(line)
-    return str(result)[:10]
+            ans += int(line)
+
+    return str(ans)[:10]
 
 
 if __name__ == "__main__":
-
-    print(f"Result for Problem 13: {compute()}")
+    print(f"Result for Problem 13 is {compute()}")