ch21 cleanup, f-strings, and pathlib

21-futures/demo_executor_map.py

@@ -24,7 +24,7 @@ def main():
     display('results:', results)  # <6>
     display('Waiting for individual results:')
     for i, result in enumerate(results):  # <7>
-        display('result {}: {}'.format(i, result))
+        display(f'result {i}: {result}')
 
 if __name__ == '__main__':
     main()

21-futures/getflags/flags.py

@@ -17,8 +17,8 @@ Sample runs (first with new domain, so no caching ever)::
 """
 
 # tag::FLAGS_PY[]
-import os
 import time
+from pathlib import Path
 from typing import Callable
 
 import requests  # <1>
@@ -27,12 +27,10 @@ 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>
+DEST_DIR = Path('downloaded')                         # <4>
 
 def save_flag(img: bytes, filename: str) -> None:     # <5>
-    path = os.path.join(DEST_DIR, filename)
+    (DEST_DIR / filename).write_bytes(img)
-    with open(path, 'wb') as fp:
-        fp.write(img)
 
 def get_flag(cc: str) -> bytes:  # <6>
     cc = cc.lower()
@@ -45,7 +43,6 @@ def download_many(cc_list: list[str]) -> int:  # <7>
         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>

21-futures/getflags/flags2_asyncio.py

@@ -28,7 +28,8 @@ class FetchError(Exception):  # <1>
 
 
 async def get_flag(session, base_url, cc):  # <2>
-    url = '{}/{cc}/{cc}.gif'.format(base_url, cc=cc.lower())
+    cc = cc.lower()
+    url = f'{base_url}/{cc}/{cc}.gif'
     async with session.get(url) as resp:
         if resp.status == 200:
             return await resp.read()
@@ -87,8 +88,7 @@ async def downloader_coro(cc_list: list[str],
                 except IndexError:
                     error_msg = exc.__cause__.__class__.__name__  # <11>
                 if verbose and error_msg:
-                    msg = '*** Error for {}: {}'
+                    print(f'*** Error for {country_code}: {error_msg}')
-                    print(msg.format(country_code, error_msg))
                 status = HTTPStatus.error
             else:
                 status = res.status

21-futures/getflags/flags2_common.py

@@ -1,14 +1,13 @@
 """Utilities for second set of flag examples.
 """
 
-import os
-import time
-import sys
-import string
 import argparse
+import string
+import sys
+import time
 from collections import namedtuple, Counter
 from enum import Enum
-
+from pathlib import Path
 
 Result = namedtuple('Result', 'status data')
 
@@ -28,14 +27,12 @@ SERVERS = {
 }
 DEFAULT_SERVER = 'LOCAL'
 
-DEST_DIR = 'downloaded/'
+DEST_DIR = Path('downloaded')
-COUNTRY_CODES_FILE = 'country_codes.txt'
+COUNTRY_CODES_FILE = Path('country_codes.txt')
 
 
 def save_flag(img: bytes, filename: str) -> None:
-    path = os.path.join(DEST_DIR, filename)
+    (DEST_DIR / filename).write_bytes(img)
-    with open(path, 'wb') as fp:
-        fp.write(img)
 
 
 def initial_report(cc_list: list[str],
@@ -44,30 +41,27 @@ def initial_report(cc_list: list[str],
     if len(cc_list) <= 10:
         cc_msg = ', '.join(cc_list)
     else:
-        cc_msg = 'from {} to {}'.format(cc_list[0], cc_list[-1])
+        cc_msg = f'from {cc_list[0]} to {cc_list[-1]}'
-    print('{} site: {}'.format(server_label, SERVERS[server_label]))
+    print(f'{server_label} site: {SERVERS[server_label]}')
-    msg = 'Searching for {} flag{}: {}'
     plural = 's' if len(cc_list) != 1 else ''
-    print(msg.format(len(cc_list), plural, cc_msg))
+    print(f'Searching for {len(cc_list)} flag{plural}: {cc_msg}')
     plural = 's' if actual_req != 1 else ''
-    msg = '{} concurrent connection{} will be used.'
+    print(f'{actual_req} concurrent connection{plural} will be used.')
-    print(msg.format(actual_req, plural))
 
 
 def final_report(cc_list: list[str],
                  counter: Counter[HTTPStatus],
                  start_time: float) -> None:
-    elapsed = time.time() - start_time
+    elapsed = time.perf_counter() - start_time
     print('-' * 20)
-    msg = '{} flag{} downloaded.'
     plural = 's' if counter[HTTPStatus.ok] != 1 else ''
-    print(msg.format(counter[HTTPStatus.ok], plural))
+    print(f'{counter[HTTPStatus.ok]} flag{plural} downloaded.')
     if counter[HTTPStatus.not_found]:
-        print(counter[HTTPStatus.not_found], 'not found.')
+        print(f'{counter[HTTPStatus.not_found]} not found.')
     if counter[HTTPStatus.error]:
         plural = 's' if counter[HTTPStatus.error] != 1 else ''
-        print('{} error{}.'.format(counter[HTTPStatus.error], plural))
+        print(f'{counter[HTTPStatus.error]} error{plural}')
-    print('Elapsed time: {:.2f}s'.format(elapsed))
+    print(f'Elapsed time: {elapsed:.2f}s')
 
 
 def expand_cc_args(every_cc: bool,
@@ -75,22 +69,21 @@ def expand_cc_args(every_cc: bool,
                    cc_args: list[str],
                    limit: int) -> list[str]:
     codes: set[str] = set()
-    A_Z = string.ascii_uppercase
+    A_Z = set(string.ascii_uppercase)
     if every_cc:
-        codes.update(a+b for a in A_Z for b in A_Z)
+        codes.update(f'{a}{b}' for a in A_Z for b in A_Z)
     elif all_cc:
-        with open(COUNTRY_CODES_FILE) as fp:
+        text = COUNTRY_CODES_FILE.read_text()
-            text = fp.read()
         codes.update(text.split())
     else:
         for cc in (c.upper() for c in cc_args):
             if len(cc) == 1 and cc in A_Z:
-                codes.update(cc+c for c in A_Z)
+                codes.update(cc + c for c in A_Z)
             elif len(cc) == 2 and all(c in A_Z for c in cc):
                 codes.add(cc)
             else:
-                msg = 'each CC argument must be A to Z or AA to ZZ.'
+                raise ValueError('*** Usage error: each CC argument '
-                raise ValueError('*** Usage error: '+msg)
+                                 'must be A to Z or AA to ZZ.')
     return sorted(codes)[:limit]
 
 
@@ -98,23 +91,29 @@ def process_args(default_concur_req):
     server_options = ', '.join(sorted(SERVERS))
     parser = argparse.ArgumentParser(
         description='Download flags for country codes. '
-        'Default: top 20 countries by population.')
+                    'Default: top 20 countries by population.')
-    parser.add_argument('cc', metavar='CC', nargs='*',
+    parser.add_argument(
+        'cc', metavar='CC', nargs='*',
         help='country code or 1st letter (eg. B for BA...BZ)')
-    parser.add_argument('-a', '--all', action='store_true',
+    parser.add_argument(
+        '-a', '--all', action='store_true',
         help='get all available flags (AD to ZW)')
-    parser.add_argument('-e', '--every', action='store_true',
+    parser.add_argument(
+        '-e', '--every', action='store_true',
         help='get flags for every possible code (AA...ZZ)')
-    parser.add_argument('-l', '--limit', metavar='N', type=int,
+    parser.add_argument(
-        help='limit to N first codes', default=sys.maxsize)
+        '-l', '--limit', metavar='N', type=int, help='limit to N first codes',
-    parser.add_argument('-m', '--max_req', metavar='CONCURRENT', type=int,
+        default=sys.maxsize)
+    parser.add_argument(
+        '-m', '--max_req', metavar='CONCURRENT', type=int,
         default=default_concur_req,
         help=f'maximum concurrent requests (default={default_concur_req})')
-    parser.add_argument('-s', '--server', metavar='LABEL',
+    parser.add_argument(
-        default=DEFAULT_SERVER,
+        '-s', '--server', metavar='LABEL', default=DEFAULT_SERVER,
-        help=('Server to hit; one of ' +
+        help=f'Server to hit; one of {server_options} '
-              f'{server_options} (default={DEFAULT_SERVER})'))
+             f'(default={DEFAULT_SERVER})')
-    parser.add_argument('-v', '--verbose', action='store_true',
+    parser.add_argument(
+        '-v', '--verbose', action='store_true',
         help='output detailed progress info')
     args = parser.parse_args()
     if args.max_req < 1:
@@ -127,8 +126,8 @@ def process_args(default_concur_req):
         sys.exit(1)
     args.server = args.server.upper()
     if args.server not in SERVERS:
-        print('*** Usage error: --server LABEL must be one of',
+        print(f'*** Usage error: --server LABEL '
-              server_options)
+              f'must be one of {server_options}')
         parser.print_usage()
         sys.exit(1)
     try:
@@ -148,8 +147,9 @@ def main(download_many, default_concur_req, max_concur_req):
     actual_req = min(args.max_req, max_concur_req, len(cc_list))
     initial_report(cc_list, actual_req, args.server)
     base_url = SERVERS[args.server]
-    t0 = time.time()
+    t0 = time.perf_counter()
     counter = download_many(cc_list, base_url, args.verbose, actual_req)
-    assert sum(counter.values()) == len(cc_list), \
+    assert sum(counter.values()) == len(cc_list), (
         'some downloads are unaccounted for'
+    )
     final_report(cc_list, counter, t0)

21-futures/getflags/flags2_sequential.py

@@ -24,7 +24,6 @@ import tqdm  # type: ignore
 
 from flags2_common import main, save_flag, HTTPStatus, Result
 
-
 DEFAULT_CONCUR_REQ = 1
 MAX_CONCUR_REQ = 1
 

21-futures/getflags/flags2_threadpool.py

@@ -50,8 +50,8 @@ def download_many(cc_list: list[str],
             try:
                 res = future.result()  # <14>
             except requests.exceptions.HTTPError as exc:  # <15>
-                error_msg = 'HTTP {res.status_code} - {res.reason}'
+                error_fmt = 'HTTP {res.status_code} - {res.reason}'
-                error_msg = error_msg.format(res=exc.response)
+                error_msg = error_fmt.format(res=exc.response)
             except requests.exceptions.ConnectionError:
                 error_msg = 'Connection error'
             else:
@@ -63,7 +63,7 @@ def download_many(cc_list: list[str],
             counter[status] += 1
             if verbose and error_msg:
                 cc = to_do_map[future]  # <16>
-                print('*** Error for {}: {}'.format(cc, error_msg))
+                print(f'*** Error for {cc}: {error_msg}')
 
     return counter
 

21-futures/getflags/flags_asyncio.py

@@ -18,7 +18,7 @@ from aiohttp import ClientSession  # <1>
 
 from flags import BASE_URL, save_flag, main  # <2>
 
-async def get_flag(session: ClientSession ,cc: str) -> bytes:  # <3>
+async def get_flag(session: ClientSession, cc: str) -> bytes:  # <3>
     cc = cc.lower()
     url = f'{BASE_URL}/{cc}/{cc}.gif'
     async with session.get(url) as resp:  # <4>
@@ -36,7 +36,6 @@ async def supervisor(cc_list):
         to_do = [download_one(session, cc)
                  for cc in sorted(cc_list)]  # <8>
         res = await asyncio.gather(*to_do)   # <9>
-
     return len(res)
 
 def download_many(cc_list):

21-futures/getflags/flags_threadpool.py

@@ -31,4 +31,4 @@ def download_many(cc_list: list[str]) -> int:
 
 if __name__ == '__main__':
     main(download_many)  # <6>
-# end::FLAGS_THREADPOOL[]
+# end::FLAGS_THREADPOOL[]

21-futures/getflags/flags_threadpool_futures.py

@@ -6,7 +6,7 @@ ThreadPoolExecutor example with ``as_completed``.
 """
 from concurrent import futures
 
-from flags import save_flag, main
+from flags import main
 from flags_threadpool import download_one
 
 
@@ -18,19 +18,14 @@ def download_many(cc_list: list[str]) -> int:
         for cc in sorted(cc_list):  # <3>
             future = executor.submit(download_one, cc)  # <4>
             to_do.append(future)  # <5>
-            msg = 'Scheduled for {}: {}'
+            print(f'Scheduled for {cc}: {future}')  # <6>
-            print(msg.format(cc, future))  # <6>
 
-        count = 0
+        for count, future in enumerate(futures.as_completed(to_do)):  # <7>
-        for future in futures.as_completed(to_do):  # <7>
             res: str = future.result()  # <8>
-            msg = '{} result: {!r}'
+            print(f'{future} result: {res!r}')  # <9>
-            print(msg.format(future, res)) # <9>
-            count += 1
 
     return count
 # end::FLAGS_THREADPOOL_AS_COMPLETED[]
 
 if __name__ == '__main__':
     main(download_many)
-

21-futures/getflags/slow_server.py

@@ -8,14 +8,14 @@ GET responses, and optionally returns errors to a fraction of
 the requests if given the --error_rate command-line argument.
 """
 
-import time
+import contextlib
 import os
 import socket
-import contextlib
+import time
 from functools import partial
-from random import random
 from http import server, HTTPStatus
 from http.server import ThreadingHTTPServer, SimpleHTTPRequestHandler
+from random import random
 
 
 class SlowHTTPRequestHandler(SimpleHTTPRequestHandler):
@@ -52,7 +52,6 @@ class SlowHTTPRequestHandler(SimpleHTTPRequestHandler):
 # https://github.com/python/cpython/blob/master/Lib/http/server.py
 
 if __name__ == '__main__':
-
     import argparse
 
     parser = argparse.ArgumentParser()
@@ -61,11 +60,11 @@ if __name__ == '__main__':
                              '[default: all interfaces]')
     parser.add_argument('--directory', '-d', default=os.getcwd(),
                         help='Specify alternative directory '
-                        '[default:current directory]')
+                             '[default:current directory]')
     parser.add_argument('--error-rate', '-e', metavar='PROBABILITY',
                         default=0.0, type=float,
                         help='Error rate; e.g. use .25 for 25%% probability '
-                        '[default:0.0]')
+                             '[default:0.0]')
     parser.add_argument('port', action='store',
                         default=8000, type=int,
                         nargs='?',

21-futures/primes/proc_pool.py

@@ -6,10 +6,10 @@ but using `concurrent.futures.ProcessPoolExecutor`.
 """
 
 # tag::PRIMES_POOL[]
+import sys
+from concurrent import futures  # <1>
 from time import perf_counter
 from typing import NamedTuple
-from concurrent import futures  # <1>
-import sys
 
 from primes import is_prime, NUMBERS
 
@@ -43,8 +43,8 @@ def main() -> None:
             print(f'{n:16}  {label} {elapsed:9.6f}s')
 
     time = perf_counter() - t0
-    print('Total time:', f'{time:0.2f}s')
+    print(f'Total time: {time:.2f}s')
 
 if __name__ == '__main__':
     main()
-# end::PRIMES_POOL[]
+# end::PRIMES_POOL[]