Sync binary-search with the updated tutorial (#943)

* Sync binary-search with the maintenance update of How to Do a Binary Search in Python

find_all_indices() tested the leftmost and rightmost indices for
truthiness, so a match at index 0 returned an empty set. Compare them
against None instead, matching the updated tutorial.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Keep download_imdb.py runnable on Python 3.7+

The tutorial and benchmark.py state a Python 3.7 floor, but the
parenthesized context managers in download_imdb.py need 3.9. Nested
with statements restore the stated floor (vermin: 3.7) without changing
behavior.

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: realpython-bot

binary-search/download_imdb.py

@@ -22,11 +22,9 @@ def main():
     with open("names.txt", "w", encoding="utf-8") as destination:
         destination.writelines(names())
 
-    with (
-        open("names.txt", encoding="utf-8") as source,
-        open("sorted_names.txt", "w", encoding="utf-8") as destination,
-    ):
-        destination.writelines(sorted(source.readlines()))
+    with open("names.txt", encoding="utf-8") as source:
+        with open("sorted_names.txt", "w", encoding="utf-8") as destination:
+            destination.writelines(sorted(source.readlines()))
 
     print('Created "names.txt" and "sorted_names.txt"')
 

binary-search/search/binary.py

@@ -68,7 +68,7 @@ def find_all_indices(
     left = find_leftmost_index(elements, value, key)
     right = find_rightmost_index(elements, value, key)
 
-    if left and right:
+    if left is not None and right is not None:
         return set(range(left, right + 1))
 
     return set()