ch21 examples

21-futures/getflags/flags.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+
+"""Download flags of top 20 countries by population
+
+Sequential version
+
+Sample runs (first with new domain, so no caching ever)::
+
+    $ ./flags.py
+    BD BR CD CN DE EG ET FR ID IN IR JP MX NG PH PK RU TR US VN
+    20 downloads in 26.21s
+    $ ./flags.py
+    BD BR CD CN DE EG ET FR ID IN IR JP MX NG PH PK RU TR US VN
+    20 downloads in 14.57s
+
+
+"""
+
+# tag::FLAGS_PY[]
+import os
+import time
+from typing import Callable
+
+import requests  # <1>
+
+POP20_CC = ('CN IN US ID BR PK NG BD RU JP '
+            'MX PH VN ET EG DE IR TR CD FR').split()  # <2>
+
+BASE_URL = 'http://fluentpython.com/data/flags'       # <3>
+DEST_DIR = 'downloaded/'                              # <4>
+
+def save_flag(img: bytes, filename: str) -> None:     # <5>
+    path = os.path.join(DEST_DIR, filename)
+    with open(path, 'wb') as fp:
+        fp.write(img)
+
+def get_flag(cc: str) -> bytes:  # <6>
+    cc = cc.lower()
+    url = f'{BASE_URL}/{cc}/{cc}.gif'
+    resp = requests.get(url)
+    return resp.content
+
+def download_many(cc_list: list[str]) -> int:  # <7>
+    for cc in sorted(cc_list):                 # <8>
+        image = get_flag(cc)
+        print(cc, end=' ', flush=True)         # <9>
+        save_flag(image, cc.lower() + '.gif')
+
+    return len(cc_list)
+
+def main(downloader: Callable[[list[str]], int]) -> None:  # <10>
+    t0 = time.perf_counter()                               # <11>
+    count = downloader(POP20_CC)
+    elapsed = time.perf_counter() - t0
+    print(f'\n{count} downloads in {elapsed:.2f}s')
+
+if __name__ == '__main__':
+    main(download_many)     # <12>
+# end::FLAGS_PY[]