Cleanup Project Euler Problem 01 (#2900)

* mv str statement into docstr

* rename var to avoid redefining builtin

* clean up module docstr

project_euler/problem_01/sol3.py

@@ -1,7 +1,7 @@
 """
 Problem Statement:
 If we list all the natural numbers below 10 that are multiples of 3 or 5,
-we get 3,5,6 and 9. The sum of these multiples is 23.
+we get 3, 5, 6 and 9. The sum of these multiples is 23.
 Find the sum of all the multiples of 3 or 5 below N.
 """
 
@@ -22,38 +22,38 @@ def solution(n: int = 1000) -> int:
     83700
     """
 
-    sum = 0
+    total = 0
     num = 0
     while 1:
         num += 3
         if num >= n:
             break
-        sum += num
+        total += num
         num += 2
         if num >= n:
             break
-        sum += num
+        total += num
         num += 1
         if num >= n:
             break
-        sum += num
+        total += num
         num += 3
         if num >= n:
             break
-        sum += num
+        total += num
         num += 1
         if num >= n:
             break
-        sum += num
+        total += num
         num += 2
         if num >= n:
             break
-        sum += num
+        total += num
         num += 3
         if num >= n:
             break
-        sum += num
-    return sum
+        total += num
+    return total
 
 
 if __name__ == "__main__":