updated chapter 4 and appendix-A files

appendix-A/flags2_sequential.py

@@ -0,0 +1,87 @@
+"""Download flags of countries (with error handling).
+
+Sequential version
+
+Sample run::
+
+    $ python3 flags2_sequential.py -s DELAY b
+    DELAY site: http://localhost:8002/flags
+    Searching for 26 flags: from BA to BZ
+    1 concurrent connection will be used.
+    --------------------
+    17 flags downloaded.
+    9 not found.
+    Elapsed time: 13.36s
+
+"""
+
+import collections
+
+import requests
+import tqdm
+
+from flags2_common import main, save_flag, HTTPStatus, Result
+
+
+DEFAULT_CONCUR_REQ = 1
+MAX_CONCUR_REQ = 1
+
+# BEGIN FLAGS2_BASIC_HTTP_FUNCTIONS
+def get_flag(base_url, cc):
+    url = '{}/{cc}/{cc}.gif'.format(base_url, cc=cc.lower())
+    resp = requests.get(url)
+    if resp.status_code != 200:  
+        resp.raise_for_status()
+    return resp.content
+
+
+def download_one(cc, base_url, verbose=False):
+    try:
+        image = get_flag(base_url, cc)
+    except requests.exceptions.HTTPError as exc:  
+        res = exc.response
+        if res.status_code == 404:
+            status = HTTPStatus.not_found 
+            msg = 'not found'
+        else:  
+            raise
+    else:
+        save_flag(image, cc.lower() + '.gif')
+        status = HTTPStatus.ok
+        msg = 'OK'
+
+    if verbose:  
+        print(cc, msg)
+
+    return Result(status, cc) 
+# END FLAGS2_BASIC_HTTP_FUNCTIONS
+
+# BEGIN FLAGS2_DOWNLOAD_MANY_SEQUENTIAL
+def download_many(cc_list, base_url, verbose, max_req):
+    counter = collections.Counter()  
+    cc_iter = sorted(cc_list)  
+    if not verbose:
+        cc_iter = tqdm.tqdm(cc_iter)  
+    for cc in cc_iter:  
+        try:
+            res = download_one(cc, base_url, verbose)  
+        except requests.exceptions.HTTPError as exc:  
+            error_msg = 'HTTP error {res.status_code} - {res.reason}'
+            error_msg = error_msg.format(res=exc.response)
+        except requests.exceptions.ConnectionError as exc:  
+            error_msg = 'Connection error'
+        else:  
+            error_msg = ''
+            status = res.status
+
+        if error_msg:
+            status = HTTPStatus.error  
+        counter[status] += 1  
+        if verbose and error_msg: 
+            print('*** Error for {}: {}'.format(cc, error_msg))
+
+    return counter 
+# END FLAGS2_DOWNLOAD_MANY_SEQUENTIAL
+
+if __name__ == '__main__':
+    main(download_many, DEFAULT_CONCUR_REQ, MAX_CONCUR_REQ)