diff --git a/src/requests/adapters.py b/src/requests/adapters.py
index 9a58b16025..3ec9a782a6 100644
--- a/src/requests/adapters.py
+++ b/src/requests/adapters.py
@@ -546,12 +546,9 @@ def close(self):
     def request_url(self, request, proxies):
         """Obtain the url to use when making the final request.
 
-        If the message is being sent through a HTTP proxy, the full URL has to
-        be used. Otherwise, we should only use the path portion of the URL.
+        If the message is being sent through a HTTP proxy, the full URL has to be used. Otherwise, we should only use the path portion of the URL.
 
-        This should not be called from user code, and is only exposed for use
-        when subclassing the
-        :class:`HTTPAdapter <requests.adapters.HTTPAdapter>`.
+        This should not be called from user code, and is only exposed for use when subclassing the :class:`HTTPAdapter <requests.adapters.HTTPAdapter>`.
 
         :param request: The :class:`PreparedRequest <PreparedRequest>` being sent.
         :param proxies: A dictionary of schemes or schemes and hosts to proxy URLs.
@@ -560,20 +557,13 @@ def request_url(self, request, proxies):
         proxy = select_proxy(request.url, proxies)
         scheme = urlparse(request.url).scheme
 
-        is_proxied_http_request = proxy and scheme != "https"
-        using_socks_proxy = False
-        if proxy:
+        if proxy and scheme != "https":
             proxy_scheme = urlparse(proxy).scheme.lower()
-            using_socks_proxy = proxy_scheme.startswith("socks")
-
+            if not proxy_scheme.startswith("socks"):
+                return urldefragauth(request.url)
+        
         url = request.path_url
-        if url.startswith("//"):  # Don't confuse urllib3
-            url = f"/{url.lstrip('/')}"
-
-        if is_proxied_http_request and not using_socks_proxy:
-            url = urldefragauth(request.url)
-
-        return url
+        return f"/{url.lstrip('/')}" if url.startswith("//") else url
 
     def add_headers(self, request, **kwargs):
         """Add any headers needed by the connection. As of v2.0 this does
diff --git a/src/requests/utils.py b/src/requests/utils.py
index 699683e5d9..c737fc75d3 100644
--- a/src/requests/utils.py
+++ b/src/requests/utils.py
@@ -844,24 +844,25 @@ def select_proxy(url, proxies):
     :param url: The url being for the request
     :param proxies: A dictionary of schemes or schemes and hosts to proxy URLs
     """
-    proxies = proxies or {}
+    if not proxies:
+        return None  # Early return if proxies are not provided
+  
     urlparts = urlparse(url)
-    if urlparts.hostname is None:
+    if not urlparts.hostname:
         return proxies.get(urlparts.scheme, proxies.get("all"))
 
-    proxy_keys = [
-        urlparts.scheme + "://" + urlparts.hostname,
+    proxy_keys = (
+        f"{urlparts.scheme}://{urlparts.hostname}",
         urlparts.scheme,
-        "all://" + urlparts.hostname,
+        f"all://{urlparts.hostname}",
         "all",
-    ]
-    proxy = None
+    )
+
     for proxy_key in proxy_keys:
         if proxy_key in proxies:
-            proxy = proxies[proxy_key]
-            break
+            return proxies[proxy_key]  # Early return if proxy found
 
-    return proxy
+    return None  # If no proxy is found
 
 
 def resolve_proxies(request, proxies, trust_env=True):
@@ -1072,7 +1073,6 @@ def urldefragauth(url):
     """
     scheme, netloc, path, params, query, fragment = urlparse(url)
 
-    # see func:`prepend_scheme_if_needed`
     if not netloc:
         netloc, path = path, netloc