bpo-38626: Add comment explaining why __lt__ is used. (GH-16978)

https://bugs.python.org/issue38626

Lib/bisect.py

@@ -29,6 +29,7 @@ def bisect_right(a, x, lo=0, hi=None):
         hi = len(a)
     while lo < hi:
         mid = (lo+hi)//2
+        # Use __lt__ to match the logic in list.sort() and in heapq
         if x < a[mid]: hi = mid
         else: lo = mid+1
     return lo
@@ -63,6 +64,7 @@ def bisect_left(a, x, lo=0, hi=None):
         hi = len(a)
     while lo < hi:
         mid = (lo+hi)//2
+        # Use __lt__ to match the logic in list.sort() and in heapq
         if a[mid] < x: lo = mid+1
         else: hi = mid
     return lo