final concurrency examples

futures/countries/flags_threadpool_ac.py

@@ -0,0 +1,55 @@
+"""Download flags of top 20 countries by population
+
+ThreadPoolExecutor version 2, with ``as_completed``.
+
+Sample run::
+
+    $ python3 flags_threadpool.py
+    BD retrieved.
+    EG retrieved.
+    CN retrieved.
+    ...
+    PH retrieved.
+    US retrieved.
+    IR retrieved.
+    20 flags downloaded in 0.93s
+
+"""
+from concurrent import futures
+
+from flags import save_flag, get_flag, show, main
+
+MAX_WORKERS = 20
+
+
+def download_one(cc):
+    image = get_flag(cc)
+    show(cc)
+    save_flag(image, cc.lower() + '.gif')
+    return cc
+
+
+# BEGIN FLAGS_THREADPOOL_AS_COMPLETED
+def download_many(cc_list):
+    cc_list = cc_list[:5]  # <1>
+    with futures.ThreadPoolExecutor(max_workers=3) as executor:  # <2>
+        to_do = []
+        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>
+
+        results = []
+        for future in futures.as_completed(to_do):  # <7>
+            res = future.result()  # <8>
+            msg = '{} result: {!r}'
+            print(msg.format(future, res)) # <9>
+            results.append(res)
+
+    return len(results)
+# END FLAGS_THREADPOOL_AS_COMPLETED
+
+if __name__ == '__main__':
+    main(download_many)
+