ch21 examples

21-futures/getflags/flags_threadpool_futures.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+
+"""Download flags of top 20 countries by population
+
+ThreadPoolExecutor example with ``as_completed``.
+"""
+from concurrent import futures
+
+from flags import save_flag, main
+from flags_threadpool import download_one
+
+
+# tag::FLAGS_THREADPOOL_AS_COMPLETED[]
+def download_many(cc_list: list[str]) -> int:
+    cc_list = cc_list[:5]  # <1>
+    with futures.ThreadPoolExecutor(max_workers=3) as executor:  # <2>
+        to_do: list[futures.Future] = []
+        for cc in sorted(cc_list):  # <3>
+            future = executor.submit(download_one, cc)  # <4>
+            to_do.append(future)  # <5>
+            msg = 'Scheduled for {}: {}'
+            print(msg.format(cc, future))  # <6>
+
+        count = 0
+        for future in futures.as_completed(to_do):  # <7>
+            res: str = future.result()  # <8>
+            msg = '{} result: {!r}'
+            print(msg.format(future, res)) # <9>
+            count += 1
+
+    return count
+# end::FLAGS_THREADPOOL_AS_COMPLETED[]
+
+if __name__ == '__main__':
+    main(download_many)
+