some chapter 17 examples updated for Python 3.7

17-futures-py3.7/countries/flags.py

@@ -0,0 +1,63 @@
+"""Download flags of top 20 countries by population
+
+Sequential version
+
+Sample run::
+
+    $ python3 flags.py
+    BD BR CD CN DE EG ET FR ID IN IR JP MX NG PH PK RU TR US VN
+    20 flags downloaded in 5.49s
+
+"""
+# BEGIN FLAGS_PY
+import os
+import time
+import sys
+
+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://flupy.org/data/flags'  # <3>
+
+DEST_DIR = 'downloads/'  # <4>
+
+
+def save_flag(img, filename):  # <5>
+    path = os.path.join(DEST_DIR, filename)
+    with open(path, 'wb') as fp:
+        fp.write(img)
+
+
+def get_flag(cc):  # <6>
+    url = '{}/{cc}/{cc}.gif'.format(BASE_URL, cc=cc.lower())
+    resp = requests.get(url)
+    return resp.content
+
+
+def show(text):  # <7>
+    print(text, end=' ')
+    sys.stdout.flush()
+
+
+def download_many(cc_list):  # <8>
+    for cc in sorted(cc_list):  # <9>
+        image = get_flag(cc)
+        show(cc)
+        save_flag(image, cc.lower() + '.gif')
+
+    return len(cc_list)
+
+
+def main():  # <10>
+    t0 = time.time()
+    count = download_many(POP20_CC)
+    elapsed = time.time() - t0
+    msg = '\n{} flags downloaded in {:.2f}s'
+    print(msg.format(count, elapsed))
+
+
+if __name__ == '__main__':
+    main()
+# END FLAGS_PY