Move fuel calculation to a function

2019/01b.py

     with open("01ain.txt", "r") as file:
         lines = file.readlines()
     masses = [int(x) for x in lines]
-    fuels = [(x//3) - 2 for x in masses]
+    fuels = [getFuel(x) for x in masses]
     newfuels = []
     for fuel in fuels:
         of = fuel
         f = fuel
         while f > 0:
-            af = (f//3) - 2
-            if af > 0:
-                of += af
-                f = af
-            else:
-                f = 0
+            f = getFuel(f)
+            of += f
         newfuels.append(of)
     #print(newfuels)
     print(sum(newfuels))
 
+def getFuel(f):
+    fuel = (f//3) - 2
+    if fuel > 0:
+        return fuel
+    return 0
+
 if __name__ == "__main__":
     main()