refactor: replace string concatenations with f-strings

server.py

@@ -32,9 +32,9 @@ def youtu_be(env, start_response):
     id = env['PATH_INFO'][1:]
     env['PATH_INFO'] = '/watch'
     if not env['QUERY_STRING']:
-        env['QUERY_STRING'] = 'v=' + id
+        env['QUERY_STRING'] = f'v={id}'
     else:
-        env['QUERY_STRING'] += '&v=' + id
+        env['QUERY_STRING'] += f'&v={id}'
     yield from yt_app(env, start_response)
 
 
@@ -64,12 +64,12 @@ def proxy_site(env, start_response, video=False):
     if 'HTTP_RANGE' in env:
         send_headers['Range'] = env['HTTP_RANGE']
 
-    url = "https://" + env['SERVER_NAME'] + env['PATH_INFO']
+    url = f"https://{env['SERVER_NAME']}{env['PATH_INFO']}"
     # remove /name portion
     if video and '/videoplayback/name/' in url:
         url = url[0:url.rfind('/name/')]
     if env['QUERY_STRING']:
-        url += '?' + env['QUERY_STRING']
+        url += f'?{env["QUERY_STRING"]}'
 
     try_num = 1
     first_attempt = True
@@ -96,7 +96,7 @@ def proxy_site(env, start_response, video=False):
                                 +[('Access-Control-Allow-Origin', '*')])
 
         if first_attempt:
-            start_response(str(response.status) + ' ' + response.reason,
+            start_response(f"{response.status} {response.reason}",
                            response_headers)
 
         content_length = int(dict(response_headers).get('Content-Length', 0))
@@ -136,9 +136,8 @@ def proxy_site(env, start_response, video=False):
                     fail_byte = start + total_received
                     send_headers['Range'] = 'bytes=%d-%d' % (fail_byte, end)
                     print(
-                        'Warning: YouTube closed the connection before byte',
-                        str(fail_byte) + '.', 'Expected', start+content_length,
-                        'bytes.'
+                        f'Warning: YouTube closed the connection before byte {fail_byte}. '
+                        f'Expected {start+content_length} bytes.'
                     )
 
                     retry = True
@@ -185,7 +184,7 @@ def split_url(url):
     # python STILL doesn't have a proper regular expression engine like grep uses built in...
     match = re.match(r'(?:https?://)?([\w-]+(?:\.[\w-]+)+?)(/.*|$)', url)
     if match is None:
-        raise ValueError('Invalid or unsupported url: ' + url)
+        raise ValueError(f'Invalid or unsupported url: {url}')
 
     return match.group(1), match.group(2)
 
@@ -238,7 +237,7 @@ def site_dispatch(env, start_response):
             if base_name == '':
                 base_name = domain
             else:
-                base_name = domain + '.' + base_name
+                base_name = f"{domain}.{base_name}"
 
             try:
                 handler = site_handlers[base_name]