diff --git a/stripe/http_client.py b/stripe/http_client.py
index f6a944df0..320089845 100644
--- a/stripe/http_client.py
+++ b/stripe/http_client.py
@@ -94,9 +94,9 @@ class HTTPClient(object):
     def __init__(self, verify_ssl_certs=True, proxy=None):
         self._verify_ssl_certs = verify_ssl_certs
         if proxy:
-            if type(proxy) is str:
+            if isinstance(proxy, str):
                 proxy = {"http": proxy, "https": proxy}
-            if not (type(proxy) is dict):
+            if not isinstance(proxy, dict):
                 raise ValueError(
                     "Proxy(ies) must be specified as either a string "
                     "URL or a dict() with string URL under the"
diff --git a/stripe/oauth.py b/stripe/oauth.py
index a25deafcb..027679389 100644
--- a/stripe/oauth.py
+++ b/stripe/oauth.py
@@ -39,16 +39,14 @@ def authorize_url(**params):
     @staticmethod
     def token(**params):
         requestor = api_requestor.APIRequestor(api_base=connect_api_base)
-        response, api_key = requestor.request(
-            "post", "/oauth/token", params, None
-        )
+        response, _ = requestor.request("post", "/oauth/token", params, None)
         return response.data
 
     @staticmethod
     def deauthorize(**params):
         requestor = api_requestor.APIRequestor(api_base=connect_api_base)
         OAuth._set_client_id(params)
-        response, api_key = requestor.request(
+        response, _ = requestor.request(
             "post", "/oauth/deauthorize", params, None
         )
         return response.data
diff --git a/stripe/util.py b/stripe/util.py
index b919c4b01..9076fc96d 100644
--- a/stripe/util.py
+++ b/stripe/util.py
@@ -225,7 +225,7 @@ def convert_to_stripe_object(
 ):
     global OBJECT_CLASSES
 
-    if len(OBJECT_CLASSES) == 0:
+    if not OBJECT_CLASSES:
         load_object_classes()
     types = OBJECT_CLASSES.copy()
 
diff --git a/stripe/webhook.py b/stripe/webhook.py
index 10fc9d470..f4d4e4f62 100644
--- a/stripe/webhook.py
+++ b/stripe/webhook.py
@@ -60,7 +60,7 @@ def verify_header(cls, payload, header, secret, tolerance=None):
                 payload,
             )
 
-        if len(signatures) == 0:
+        if not signatures:
             raise error.SignatureVerificationError(
                 "No signatures found with expected scheme "
                 "%s" % cls.EXPECTED_SCHEME,