ch21 examples

21-futures/getflags/flags_threadpool.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+
+"""Download flags of top 20 countries by population
+
+ThreadPoolExecutor version
+
+Sample run::
+
+    $ python3 flags_threadpool.py
+    DE FR BD CN EG RU IN TR VN ID JP BR NG MX PK ET PH CD US IR
+    20 downloads in 0.35s
+
+"""
+
+# tag::FLAGS_THREADPOOL[]
+from concurrent import futures
+
+from flags import save_flag, get_flag, main  # <1>
+
+def download_one(cc: str):  # <2>
+    image = get_flag(cc)
+    print(cc, end=' ', flush=True)
+    save_flag(image, cc.lower() + '.gif')
+    return cc
+
+def download_many(cc_list: list[str]) -> int:
+    with futures.ThreadPoolExecutor() as executor:         # <3>
+        res = executor.map(download_one, sorted(cc_list))  # <4>
+
+    return len(list(res))                                  # <5>
+
+if __name__ == '__main__':
+    main(download_many)  # <6>
+# end::FLAGS_THREADPOOL[]