python: Simplify with str.removeprefix, str.removesuffix.

These are available in Python ≥ 3.9.
https://docs.python.org/3/library/stdtypes.html#str.removeprefix

Signed-off-by: Anders Kaseorg <anders@zulip.com>

analytics/views/stats.py

@@ -610,7 +610,7 @@ def client_label_map(name: str) -> str:
     if name in ["ZulipPython", "API: Python"]:
         return "Python API"
     if name.startswith("Zulip") and name.endswith("Webhook"):
-        return name[len("Zulip") : -len("Webhook")] + " webhook"
+        return name.removeprefix("Zulip").removesuffix("Webhook") + " webhook"
     return name
 
 

corporate/lib/decorator.py

@@ -135,10 +135,7 @@ def get_next_page_param_from_request_path(request: HttpRequest) -> str | None:
     # Therefore we can use this nice property to figure out easily what
     # kind of page the user is trying to access and find the right value
     # for the `next` query parameter.
-    path = request.path
-    if path.endswith("/"):
-        path = path[:-1]
-
+    path = request.path.removesuffix("/")
     page_type = path.split("/")[-1]
 
     from corporate.views.remote_billing_page import (

corporate/tests/test_stripe.py

@@ -120,15 +120,16 @@ def stripe_fixture_path(
 ) -> str:
     # Make the eventual filename a bit shorter, and also we conventionally
     # use test_* for the python test files
-    if decorated_function_name[:5] == "test_":
-        decorated_function_name = decorated_function_name[5:]
-    return f"{STRIPE_FIXTURES_DIR}/{decorated_function_name}--{mocked_function_name[7:]}.{call_count}.json"
+    decorated_function_name = decorated_function_name.removeprefix("test_")
+    mocked_function_name = mocked_function_name.removeprefix("stripe.")
+    return (
+        f"{STRIPE_FIXTURES_DIR}/{decorated_function_name}--{mocked_function_name}.{call_count}.json"
+    )
 
 
 def fixture_files_for_function(decorated_function: CallableT) -> list[str]:  # nocoverage
     decorated_function_name = decorated_function.__name__
-    if decorated_function_name[:5] == "test_":
-        decorated_function_name = decorated_function_name[5:]
+    decorated_function_name = decorated_function_name.removeprefix("test_")
     return sorted(
         f"{STRIPE_FIXTURES_DIR}/{f}"
         for f in os.listdir(STRIPE_FIXTURES_DIR)

scripts/lib/sharding.py

@@ -54,7 +54,7 @@ def write_updated_configs() -> None:
         ).strip()
         for key, shards in config_file["tornado_sharding"].items():
             if key.endswith("_regex"):
-                ports = [int(port) for port in key[: -len("_regex")].split("_")]
+                ports = [int(port) for port in key.removesuffix("_regex").split("_")]
                 shard_regexes.append((shards, ports[0] if len(ports) == 1 else ports))
                 nginx_sharding_conf_f.write(
                     f"    {nginx_quote('~*' + shards)} http://tornado{'_'.join(map(str, ports))};\n"

scripts/lib/supervisor.py

@@ -58,7 +58,8 @@ def list_supervisor_processes(
             for filter_name in filter_names:
                 # zulip-tornado:* matches zulip-tornado:9800 and zulip-tornado
                 if filter_name.endswith(":*") and (
-                    name.startswith(filter_name[:-1]) or name == filter_name[:-2]
+                    name.startswith(filter_name.removesuffix("*"))
+                    or name == filter_name.removesuffix(":*")
                 ):
                     match = True
                     break

scripts/lib/upgrade-zulip-from-git

@@ -122,7 +122,7 @@ try:
         keep_refs = set()
         for worktree_line in worktree_data:
             if worktree_line.startswith("branch "):
-                keep_refs.add(worktree_line[len("branch ") :])
+                keep_refs.add(worktree_line.removeprefix("branch "))
 
         delete_input = "".join(
             f"delete {refname}\n" for refname in matching_refs if refname not in keep_refs

scripts/lib/zulip_tools.py

@@ -639,7 +639,7 @@ def get_tornado_ports(config_file: configparser.RawConfigParser) -> list[int]:
             {
                 int(port)
                 for key in config_file.options("tornado_sharding")
-                for port in (key[: -len("_regex")] if key.endswith("_regex") else key).split("_")
+                for port in key.removesuffix("_regex").split("_")
             }
         )
     if not ports:

scripts/log-search

@@ -454,9 +454,9 @@ def print_line(
         ts = match["time"]
 
     if match["duration"].endswith("ms"):
-        duration_ms = int(match["duration"][:-2])
+        duration_ms = int(match["duration"].removesuffix("ms"))
     else:
-        duration_ms = int(float(match["duration"][:-1]) * 1000)
+        duration_ms = int(float(match["duration"].removesuffix("s")) * 1000)
 
     code = int(match["code"])
     indicator = " "

tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py

@@ -165,8 +165,8 @@ class BaseDocumentationSpider(scrapy.Spider):
             if split_url.hostname == "github.com" and f"{split_url.path}/".startswith(
                 f"{ZULIP_SERVER_GITHUB_FILE_PATH_PREFIX}/"
             ):
-                file_path = (
-                    DEPLOY_ROOT + split_url.path[len(ZULIP_SERVER_GITHUB_FILE_PATH_PREFIX) :]
+                file_path = DEPLOY_ROOT + split_url.path.removeprefix(
+                    ZULIP_SERVER_GITHUB_FILE_PATH_PREFIX
                 )
                 if not os.path.isfile(file_path):
                     self.logger.error(
@@ -176,8 +176,8 @@ class BaseDocumentationSpider(scrapy.Spider):
             elif split_url.hostname == "github.com" and f"{split_url.path}/".startswith(
                 f"{ZULIP_SERVER_GITHUB_DIRECTORY_PATH_PREFIX}/"
             ):
-                dir_path = (
-                    DEPLOY_ROOT + split_url.path[len(ZULIP_SERVER_GITHUB_DIRECTORY_PATH_PREFIX) :]
+                dir_path = DEPLOY_ROOT + split_url.path.removeprefix(
+                    ZULIP_SERVER_GITHUB_DIRECTORY_PATH_PREFIX
                 )
                 if not os.path.isdir(dir_path):
                     self.logger.error(

tools/lib/provision_inner.py

@@ -37,7 +37,7 @@ UUID_VAR_PATH = get_dev_uuid_var_path()
 with get_tzdata_zi() as f:
     line = f.readline()
     assert line.startswith("# version ")
-    timezones_version = line[len("# version ") :]
+    timezones_version = line.removeprefix("# version ")
 
 
 def create_var_directories() -> None:

tools/lib/template_parser.py

@@ -186,9 +186,7 @@ def tokenize(text: str, template_format: str | None = None) -> list[Token]:
                 kind = "handlebars_else"
             elif looking_at_handlebars_start():
                 s = get_handlebars_tag(text, state.i)
-                tag = s[3:-2].split()[0].strip("#")
-                if tag.startswith("*"):
-                    tag = tag[1:]
+                tag = s[3:-2].split()[0].strip("#").removeprefix("*")
                 kind = "handlebars_start"
             elif looking_at_handlebars_end():
                 s = get_handlebars_tag(text, state.i)

tools/screenshots/generate-integration-docs-screenshot

@@ -120,8 +120,7 @@ def get_requests_headers(integration_name: str, fixture_name: str) -> dict[str,
     headers = get_fixture_http_headers(integration_name, fixture_name)
 
     def fix_name(header: str) -> str:
-        header = header if not header.startswith("HTTP_") else header[len("HTTP_") :]
-        return header.replace("_", "-")
+        return header.removeprefix("HTTP_").replace("_", "-")
 
     return {fix_name(k): v for k, v in headers.items()}
 

tools/upload-release

@@ -50,7 +50,7 @@ print("Fetching existing hashes..")
 for obj_summary in bucket.objects.filter(Prefix="server/zulip-server-"):
     head = client.head_object(Bucket=bucket.name, Key=obj_summary.key)
     assert obj_summary.key.startswith("server/")
-    filename = obj_summary.key[len("server/") :]
+    filename = obj_summary.key.removeprefix("server/")
     if filename in file_hashes:
         print(f"  {filename} was already uploaded, skipping existing hash")
         continue

zerver/lib/cache.py

@@ -78,7 +78,7 @@ def get_or_create_key_prefix() -> str:
         tries = 1
         while tries < 10:
             with open(filename) as f:
-                prefix = f.readline()[:-1]
+                prefix = f.readline().removesuffix("\n")
             if len(prefix) == 33:
                 break
             tries += 1
@@ -214,7 +214,7 @@ def cache_get_many(keys: list[str], cache_name: str | None = None) -> dict[str,
     remote_cache_stats_start()
     ret = get_cache_backend(cache_name).get_many(keys)
     remote_cache_stats_finish()
-    return {key[len(KEY_PREFIX) :]: value for key, value in ret.items()}
+    return {key.removeprefix(KEY_PREFIX): value for key, value in ret.items()}
 
 
 def safe_cache_get_many(keys: list[str], cache_name: str | None = None) -> dict[str, Any]:

zerver/lib/email_mirror.py

@@ -44,7 +44,7 @@ def redact_email_address(error_message: str) -> str:
         domain = Address(addr_spec=settings.EMAIL_GATEWAY_PATTERN).domain
     else:
         # EMAIL_GATEWAY_EXTRA_PATTERN_HACK is of the form '@example.com'
-        domain = settings.EMAIL_GATEWAY_EXTRA_PATTERN_HACK[1:]
+        domain = settings.EMAIL_GATEWAY_EXTRA_PATTERN_HACK.removeprefix("@")
 
     def redact(address_match: Match[str]) -> str:
         email_address = address_match[0]

zerver/lib/github.py

@@ -54,8 +54,7 @@ def get_latest_github_release_download_link_for_platform(platform: str) -> str:
 
     latest_version = get_latest_github_release_version_for_repo("zulip-desktop")
     if latest_version:
-        if latest_version[0] in ["v", "V"]:
-            latest_version = latest_version[1:]
+        latest_version = latest_version.removeprefix("v")
         setup_file = PLATFORM_TO_SETUP_FILE[platform].format(version=latest_version)
         link = f"https://desktop-download.zulip.com/v{latest_version}/{setup_file}"
         if verify_release_download_link(link):

zerver/lib/markdown/__init__.py

@@ -269,7 +269,7 @@ def rewrite_local_links_to_relative(db_data: DbData | None, link: str) -> str:
     if db_data:
         realm_url_prefix = db_data.realm_url + "/"
         if link.startswith((realm_url_prefix + "#", realm_url_prefix + "user_uploads/")):
-            return link[len(realm_url_prefix) :]
+            return link.removeprefix(realm_url_prefix)
 
     return link
 
@@ -622,7 +622,7 @@ class InlineInterestingLinkProcessor(markdown.treeprocessors.Treeprocessor):
             a.set("data-id", data_id)
         img = SubElement(a, "img")
         if image_url.startswith("/user_uploads/") and self.zmd.zulip_db_data:
-            path_id = image_url[len("/user_uploads/") :]
+            path_id = image_url.removeprefix("/user_uploads/")
 
             # We should have pulled the preview data for this image
             # (even if that's "no preview yet") from the database
@@ -737,7 +737,7 @@ class InlineInterestingLinkProcessor(markdown.treeprocessors.Treeprocessor):
         # a row for the ImageAttachment, then its header didn't parse
         # as a valid image type which libvips handles.
         if url.startswith("/user_uploads/") and self.zmd.zulip_db_data:
-            path_id = url[len("/user_uploads/") :]
+            path_id = url.removeprefix("/user_uploads/")
             return path_id in self.zmd.zulip_db_data.user_upload_previews
 
         return any(parsed_url.path.lower().endswith(ext) for ext in IMAGE_EXTENSIONS)
@@ -825,7 +825,7 @@ class InlineInterestingLinkProcessor(markdown.treeprocessors.Treeprocessor):
                 elif split_url.path.startswith(("/embed/", "/shorts/", "/v/")):
                     id = split_url.path.split("/", 3)[2]
             elif split_url.hostname == "youtu.be" and split_url.path.startswith("/"):
-                id = split_url.path[len("/") :]
+                id = split_url.path.removeprefix("/")
 
         if id is not None and re.fullmatch(r"[0-9A-Za-z_-]+", id):
             return id
@@ -1274,7 +1274,7 @@ class InlineInterestingLinkProcessor(markdown.treeprocessors.Treeprocessor):
                 if not parsed_url.path.startswith("/user_uploads/"):
                     continue
 
-                path_id = parsed_url.path[len("/user_uploads/") :]
+                path_id = parsed_url.path.removeprefix("/user_uploads/")
                 self.zmd.zulip_rendering_result.potential_attachment_path_ids.append(path_id)
 
         if len(found_urls) == 0:

zerver/lib/markdown/api_arguments_table_generator.py

@@ -299,9 +299,7 @@ def makeExtension(*args: Any, **kwargs: str) -> MarkdownArgumentsTableGenerator:
 def generate_data_type(schema: Mapping[str, Any]) -> str:
     data_type = ""
     if "oneOf" in schema:
-        for item in schema["oneOf"]:
-            data_type = data_type + generate_data_type(item) + " | "
-        data_type = data_type[:-3]
+        data_type = " | ".join(generate_data_type(item) for item in schema["oneOf"])
     elif "items" in schema:
         data_type = "(" + generate_data_type(schema["items"]) + ")[]"
     else:

zerver/lib/markdown/static.py

@@ -29,7 +29,7 @@ class StaticImageProcessor(markdown.treeprocessors.Treeprocessor):
         for img in root.iter("img"):
             url = img.get("src")
             if url is not None and url.startswith("/static/"):
-                img.set("src", staticfiles_storage.url(url[len("/static/") :]))
+                img.set("src", staticfiles_storage.url(url.removeprefix("/static/")))
 
 
 def makeExtension(*args: Any, **kwargs: str) -> MarkdownStaticImagesGenerator:

zerver/lib/name_restrictions.py

@@ -9,11 +9,11 @@ def is_reserved_subdomain(subdomain: str) -> bool:
         return True
     if subdomain in ZULIP_RESERVED_SUBDOMAINS:
         return True
-    if subdomain[-1] == "s" and subdomain[:-1] in ZULIP_RESERVED_SUBDOMAINS:
+    if subdomain.endswith("s") and subdomain.removesuffix("s") in ZULIP_RESERVED_SUBDOMAINS:
         return True
     if subdomain in GENERIC_RESERVED_SUBDOMAINS:
         return True
-    if subdomain[-1] == "s" and subdomain[:-1] in GENERIC_RESERVED_SUBDOMAINS:
+    if subdomain.endswith("s") and subdomain.removesuffix("s") in GENERIC_RESERVED_SUBDOMAINS:
         return True
     if settings.CORPORATE_ENABLED and ("zulip" in subdomain or "kandra" in subdomain):
         return True

zerver/lib/test_classes.py

@@ -1647,7 +1647,7 @@ Output:
             # as the actual value of the attribute in LDAP.
             for attr, value in attrs.items():
                 if isinstance(value, str) and value.startswith("file:"):
-                    with open(value[5:], "rb") as f:
+                    with open(value.removeprefix("file:"), "rb") as f:
                         attrs[attr] = [f.read()]
 
         ldap_patcher = mock.patch("django_auth_ldap.config.ldap.initialize")

zerver/lib/test_helpers.py

@@ -489,14 +489,10 @@ def write_instrumentation_reports(full_suite: bool, include_webhooks: bool) -> N
                 find_pattern(pattern, prefixes)
 
         def cleanup_url(url: str) -> str:
-            if url.startswith("/"):
-                url = url[1:]
-            if url.startswith("http://testserver/"):
-                url = url[len("http://testserver/") :]
-            if url.startswith("http://zulip.testserver/"):
-                url = url[len("http://zulip.testserver/") :]
-            if url.startswith("http://testserver:9080/"):
-                url = url[len("http://testserver:9080/") :]
+            url = url.removeprefix("/")
+            url = url.removeprefix("http://testserver/")
+            url = url.removeprefix("http://zulip.testserver/")
+            url = url.removeprefix("http://testserver:9080/")
             return url
 
         def find_pattern(pattern: Any, prefixes: list[str]) -> None:
@@ -516,7 +512,7 @@ def write_instrumentation_reports(full_suite: bool, include_webhooks: bool) -> N
 
                 for prefix in prefixes:
                     if url.startswith(prefix):
-                        match_url = url[len(prefix) :]
+                        match_url = url.removeprefix(prefix)
                         if pattern.resolve(match_url):
                             if call["status_code"] in [200, 204, 301, 302]:
                                 cnt += 1

zerver/lib/test_runner.py

@@ -346,7 +346,7 @@ class Runner(DiscoverRunner):
         prefix = "unittest.loader._FailedTest."
         for test_name in get_test_names(suite):
             if test_name.startswith(prefix):
-                test_name = test_name[len(prefix) :]
+                test_name = test_name.removeprefix(prefix)
                 for label in test_labels:
                     # This code block is for when a test label is
                     # directly provided, for example:

zerver/lib/thumbnail.py

@@ -426,7 +426,7 @@ def rewrite_thumbnailed_images(
             # second image, the first image will have no placeholder.
             continue
 
-        path_id = image_link["href"][len("/user_uploads/") :]
+        path_id = image_link["href"].removeprefix("/user_uploads/")
         if to_delete and path_id in to_delete:
             # This was not a valid thumbnail target, for some reason.
             # Trim out the whole "message_inline_image" element, since

zerver/lib/topic.py

@@ -294,7 +294,7 @@ def get_topic_resolution_and_bare_name(stored_name: str) -> tuple[bool, str]:
     - The topic name with the resolution prefix, if present in stored_name, removed
     """
     if stored_name.startswith(RESOLVED_TOPIC_PREFIX):
-        return (True, stored_name[len(RESOLVED_TOPIC_PREFIX) :])
+        return (True, stored_name.removeprefix(RESOLVED_TOPIC_PREFIX))
 
     return (False, stored_name)
 

zerver/lib/upload/local.py

@@ -239,7 +239,7 @@ class LocalUploadBackend(ZulipUploadBackend):
     def delete_export_tarball(self, export_path: str) -> str | None:
         # Get the last element of a list in the form ['user_avatars', '<file_path>']
         assert export_path.startswith("/")
-        file_path = export_path[1:].split("/", 1)[-1]
+        file_path = export_path.removeprefix("/").split("/", 1)[-1]
         if delete_local_file("avatars", file_path):
             return export_path
         return None

zerver/lib/upload/s3.py

@@ -183,7 +183,7 @@ class S3UploadBackend(ZulipUploadBackend):
         assert split_url.path.endswith(f"/{DUMMY_KEY}")
 
         return urlunsplit(
-            (split_url.scheme, split_url.netloc, split_url.path[: -len(DUMMY_KEY)], "", "")
+            (split_url.scheme, split_url.netloc, split_url.path.removesuffix(DUMMY_KEY), "", "")
         )
 
     @override
@@ -395,7 +395,7 @@ class S3UploadBackend(ZulipUploadBackend):
     @override
     def get_export_tarball_url(self, realm: Realm, export_path: str) -> str:
         # export_path has a leading /
-        return self.get_public_upload_url(export_path[1:])
+        return self.get_public_upload_url(export_path.removeprefix("/"))
 
     @override
     def upload_export_tarball(
@@ -420,7 +420,7 @@ class S3UploadBackend(ZulipUploadBackend):
     @override
     def delete_export_tarball(self, export_path: str) -> str | None:
         assert export_path.startswith("/")
-        path_id = export_path[1:]
+        path_id = export_path.removeprefix("/")
         if self.delete_file_from_s3(path_id, self.avatar_bucket):
             return export_path
         return None

zerver/lib/widget.py

@@ -12,7 +12,7 @@ def get_widget_data(content: str) -> tuple[str | None, Any]:
 
     # tokens[0] will always exist
     if tokens[0].startswith("/"):
-        widget_type = tokens[0][1:]
+        widget_type = tokens[0].removeprefix("/")
         if widget_type in valid_widget_types:
             remaining_content = content.replace(tokens[0], "", 1)
             extra_data = get_extra_data_from_widget_type(remaining_content, widget_type)

zerver/lib/zcommand.py

@@ -22,7 +22,7 @@ def process_zcommands(content: str, user_profile: UserProfile) -> dict[str, Any]
 
     if not content.startswith("/"):
         raise JsonableError(_("There should be a leading slash in the zcommand."))
-    command = content[1:]
+    command = content.removeprefix("/")
 
     if command == "ping":
         return {}

zerver/lib/zephyr.py

@@ -14,7 +14,7 @@ def compute_mit_user_fullname(email: str) -> str:
             if hesiod_name != "":
                 return hesiod_name
         elif match_user:
-            return match_user.group(1).lower() + "@" + match_user.group(2).upper()[1:]
+            return match_user.group(1).lower() + "@" + match_user.group(2).upper().removeprefix("|")
     except DNS.Base.ServerError:
         pass
     except Exception:

zerver/migrations/0459_remove_invalid_characters_from_user_group_name.py

@@ -32,7 +32,7 @@ def remove_invalid_characters_from_user_group_name(
                 continue
 
             old_group_name = group.name
-            group.name = old_group_name[1:]
+            group.name = old_group_name.removeprefix("@")
             groups_to_update.append(group)
 
         # Fix the name of non-system groups as well.
@@ -53,7 +53,7 @@ def remove_invalid_characters_from_user_group_name(
                     )
                     if len(matching_invalid_prefix) == 0:
                         break
-                    group_name = group_name[len(matching_invalid_prefix) :]
+                    group_name = group_name.removeprefix(matching_invalid_prefix)
 
                 if len(group_name) > 0 and group_name not in existing_group_names_set:
                     group.name = group_name

zerver/openapi/javascript_examples.py

@@ -16,7 +16,7 @@ from zerver.openapi.openapi import validate_against_openapi_schema
 def test_js_bindings(client: Client) -> None:
     os.environ["ZULIP_USERNAME"] = client.email
     os.environ["ZULIP_API_KEY"] = client.api_key
-    os.environ["ZULIP_REALM"] = client.base_url[:-5]
+    os.environ["ZULIP_REALM"] = client.base_url.removesuffix("/api/")
 
     output = subprocess.check_output(
         args=["node", "--unhandled-rejections=strict", "zerver/openapi/javascript_examples.js"],

zerver/openapi/markdown_extension.py

@@ -160,7 +160,7 @@ def render_python_code_example(
         "```python",
         *config,
         # Remove one level of indentation and strip newlines
-        *(line[4:].rstrip() for snippet in snippets for line in snippet),
+        *(line.removeprefix("    ").rstrip() for snippet in snippets for line in snippet),
         "print(result)",
         "\n",
         "```",

zerver/openapi/openapi.py

@@ -443,9 +443,9 @@ def validate_test_response(request: Request, response: Response) -> bool:
     """
 
     if request.path.startswith("/json/"):
-        path = request.path[len("/json") :]
+        path = request.path.removeprefix("/json")
     elif request.path.startswith("/api/v1/"):
-        path = request.path[len("/api/v1") :]
+        path = request.path.removeprefix("/api/v1")
     else:
         return False
     assert request.method is not None
@@ -571,14 +571,14 @@ def validate_test_request(
     assert request.method is not None
     method = request.method.lower()
     if request.path.startswith("/json/"):
-        url = request.path[len("/json") :]
+        url = request.path.removeprefix("/json")
         # Some JSON endpoints have different parameters compared to
         # their `/api/v1` counterparts.
         if (url, method) in SKIP_JSON:
             return
     else:
         assert request.path.startswith("/api/v1/")
-        url = request.path[len("/api/v1") :]
+        url = request.path.removeprefix("/api/v1")
 
     # TODO: Add support for file upload endpoints that lack the /json/
     # or /api/v1/ prefix.

zerver/tests/test_realm_export.py

@@ -71,7 +71,7 @@ class RealmExportTest(ZulipTestCase):
         # Test that the file is hosted, and the contents are as expected.
         export_path = audit_log_entry.extra_data["export_path"]
         assert export_path.startswith("/")
-        path_id = export_path[1:]
+        path_id = export_path.removeprefix("/")
         self.assertEqual(bucket.Object(path_id).get()["Body"].read(), b"zulip!")
 
         result = self.client_get("/json/export/realm")

zerver/tests/test_thumbnail.py

@@ -50,12 +50,12 @@ class ThumbnailRedirectEndpointTest(ZulipTestCase):
         base = "/user_uploads/"
         self.assertEqual(base, url[: len(base)])
 
-        result = self.client_get("/thumbnail", {"url": url[1:], "size": "full"})
+        result = self.client_get("/thumbnail", {"url": url.removeprefix("/"), "size": "full"})
         self.assertEqual(result.status_code, 200)
         self.assertEqual(result.getvalue(), b"zulip!")
 
         self.login("iago")
-        result = self.client_get("/thumbnail", {"url": url[1:], "size": "full"})
+        result = self.client_get("/thumbnail", {"url": url.removeprefix("/"), "size": "full"})
         self.assertEqual(result.status_code, 403, result)
         self.assert_in_response("You are not authorized to view this file.", result)
 
@@ -92,7 +92,7 @@ class ThumbnailRedirectEndpointTest(ZulipTestCase):
             self.send_stream_message(self.example_user("hamlet"), "Denmark", body, "test")
 
             self.logout()
-            response = self.client_get("/thumbnail", {"url": url[1:], "size": "full"})
+            response = self.client_get("/thumbnail", {"url": url.removeprefix("/"), "size": "full"})
             self.assertEqual(response.status_code, 302)
             self.assertTrue(response["Location"].startswith("/accounts/login/?next="))
 
@@ -104,12 +104,12 @@ class ThumbnailRedirectEndpointTest(ZulipTestCase):
             self.send_stream_message(self.example_user("hamlet"), "web-public-stream", body, "test")
 
             self.logout()
-            response = self.client_get("/thumbnail", {"url": url[1:], "size": "full"})
+            response = self.client_get("/thumbnail", {"url": url.removeprefix("/"), "size": "full"})
             self.assertEqual(response.status_code, 200)
 
         # Deny file access since rate limited
         with ratelimit_rule(86400, 0, domain="spectator_attachment_access_by_file"):
-            response = self.client_get("/thumbnail", {"url": url[1:], "size": "full"})
+            response = self.client_get("/thumbnail", {"url": url.removeprefix("/"), "size": "full"})
             self.assertEqual(response.status_code, 302)
             self.assertTrue(response["Location"].startswith("/accounts/login/?next="))
 

zerver/tests/test_upload_s3.py

@@ -193,7 +193,7 @@ class S3Test(ZulipTestCase):
         redirect_url = response["Location"]
         path = urlsplit(redirect_url).path
         assert path.startswith("/")
-        key = path[len("/") :]
+        key = path.removeprefix("/")
         self.assertEqual(b"zulip!", bucket.Object(key).get()["Body"].read())
 
         prefix = f"/internal/s3/{settings.S3_AUTH_UPLOADS_BUCKET}.s3.amazonaws.com/"
@@ -202,7 +202,7 @@ class S3Test(ZulipTestCase):
         redirect_url = response["X-Accel-Redirect"]
         path = urlsplit(redirect_url).path
         assert path.startswith(prefix)
-        key = path[len(prefix) :]
+        key = path.removeprefix(prefix)
         self.assertEqual(b"zulip!", bucket.Object(key).get()["Body"].read())
 
         # Check the download endpoint
@@ -212,7 +212,7 @@ class S3Test(ZulipTestCase):
         redirect_url = response["X-Accel-Redirect"]
         path = urlsplit(redirect_url).path
         assert path.startswith(prefix)
-        key = path[len(prefix) :]
+        key = path.removeprefix(prefix)
         self.assertEqual(b"zulip!", bucket.Object(key).get()["Body"].read())
 
         # Now try the endpoint that's supposed to return a temporary URL for access
@@ -232,7 +232,7 @@ class S3Test(ZulipTestCase):
         redirect_url = response["X-Accel-Redirect"]
         path = urlsplit(redirect_url).path
         assert path.startswith(prefix)
-        key = path[len(prefix) :]
+        key = path.removeprefix(prefix)
         self.assertEqual(b"zulip!", bucket.Object(key).get()["Body"].read())
 
         # The original url shouldn't work when logged out:
@@ -279,7 +279,7 @@ class S3Test(ZulipTestCase):
         self.assertEqual(base, url[: len(base)])
 
         # Try hitting the equivalent `/user_avatars` endpoint
-        wrong_url = "/user_avatars/" + url[len(base) :]
+        wrong_url = "/user_avatars/" + url.removeprefix(base)
         result = self.client_get(wrong_url)
         self.assertEqual(result.status_code, 301)
         self.assertEqual(result["Location"], url)

zerver/views/development/integrations.py

@@ -94,9 +94,7 @@ def get_fixtures(request: HttpRequest, *, integration_name: PathOnly[str]) -> Ht
         )
 
         def fix_name(header: str) -> str:  # nocoverage
-            if header.startswith("HTTP_"):  # HTTP_ is a prefix intended for Django.
-                return header[len("HTTP_") :]
-            return header
+            return header.removeprefix("HTTP_")  # HTTP_ is a prefix intended for Django.
 
         headers = {fix_name(k): v for k, v in headers_raw.items()}
         fixtures[fixture] = {"body": body, "headers": headers}

zerver/views/documentation.py

@@ -382,7 +382,8 @@ def integration_doc(request: HttpRequest, *, integration_name: PathOnly[str]) ->
     context["integration_display_name"] = integration.display_name
     context["recommended_channel_name"] = integration.stream_name
     if isinstance(integration, WebhookIntegration):
-        context["integration_url"] = integration.url[3:]
+        assert integration.url.startswith("api/")
+        context["integration_url"] = integration.url.removeprefix("api")
         all_event_types = get_all_event_types_for_integration(integration)
         if all_event_types is not None:
             context["all_event_types"] = all_event_types

zerver/views/message_send.py

@@ -105,8 +105,7 @@ def same_realm_irc_user(user_profile: UserProfile, email: str) -> bool:
         return False
 
     domain = Address(addr_spec=email).domain.lower()
-    if domain.startswith("irc."):
-        domain = domain[len("irc.") :]
+    domain = domain.removeprefix("irc.")
 
     # Assumes allow_subdomains=False for all RealmDomain's corresponding to
     # these realms.

zerver/webhooks/bitbucket3/view.py

@@ -92,9 +92,9 @@ def repo_comment_handler(
     repo_name = payload["repository"]["name"].tame(check_string)
     topic_name = BITBUCKET_TOPIC_TEMPLATE.format(repository_name=repo_name)
     sha = payload["commit"].tame(check_string)
-    commit_url = payload["repository"]["links"]["self"][0]["href"].tame(check_string)[
-        : -len("browse")
-    ]
+    commit_url = (
+        payload["repository"]["links"]["self"][0]["href"].tame(check_string).removesuffix("browse")
+    )
     commit_url += f"commits/{sha}"
     message = payload["comment"]["text"].tame(check_string)
     if action == "deleted their comment":

zerver/webhooks/greenhouse/view.py

@@ -26,7 +26,7 @@ def dict_list_to_string(some_list: WildValue) -> str:
         elif item_type and item_url:
             internal_template += f"[{item_type}]({item_url}), "
 
-    internal_template = internal_template[:-2]
+    internal_template = internal_template.removesuffix(", ")
     return internal_template