diff --git a/puppet/zulip/files/nagios_plugins/zulip_app_frontend/check_send_receive_time b/puppet/zulip/files/nagios_plugins/zulip_app_frontend/check_send_receive_time
index 89f4c8a403..6c762d96ff 100755
--- a/puppet/zulip/files/nagios_plugins/zulip_app_frontend/check_send_receive_time
+++ b/puppet/zulip/files/nagios_plugins/zulip_app_frontend/check_send_receive_time
@@ -155,7 +155,7 @@ send_zulip(zulip_sender, {
     "to": recipient.email,
 })
 
-msg_content = []  # type: List[str]
+msg_content: List[str] = []
 
 while msg_to_send not in msg_content:
     messages = get_zulips()
diff --git a/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_personal_zephyr_mirrors b/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_personal_zephyr_mirrors
index f9ea4383df..3187b2a5b6 100755
--- a/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_personal_zephyr_mirrors
+++ b/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_personal_zephyr_mirrors
@@ -12,14 +12,14 @@ from typing import Dict
 import os
 import time
 
-RESULTS_DIR = "/home/zulip/mirror_status"  # type: str
+RESULTS_DIR: str = "/home/zulip/mirror_status"
 
-states = {
+states: Dict[str, int] = {
     "OK": 0,
     "WARNING": 1,
     "CRITICAL": 2,
     "UNKNOWN": 3
-}  # type: Dict[str, int]
+}
 
 def report(state: str, output: str) -> None:
     print("%s\n%s" % (state, output))
diff --git a/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_user_zephyr_mirror_liveness b/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_user_zephyr_mirror_liveness
index 3b16960ddf..d518b6a2ca 100755
--- a/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_user_zephyr_mirror_liveness
+++ b/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_user_zephyr_mirror_liveness
@@ -28,12 +28,12 @@ from zerver.models import UserActivity
 
 from typing import Any, Dict, Set, Optional
 
-states = {
+states: Dict[str, int] = {
     "OK": 0,
     "WARNING": 1,
     "CRITICAL": 2,
     "UNKNOWN": 3
-}  # type: Dict[str, int]
+}
 
 def report(state: str, short_msg: str, too_old: Optional[Set[Any]] = None) -> None:
     too_old_data = ""
diff --git a/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_zephyr_mirror b/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_zephyr_mirror
index b608bab6d8..fff7cef75a 100755
--- a/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_zephyr_mirror
+++ b/puppet/zulip_ops/files/nagios_plugins/zulip_zephyr_mirror/check_zephyr_mirror
@@ -15,12 +15,12 @@ import time
 
 RESULTS_FILE = "/var/lib/nagios_state/check-mirroring-results"
 
-states = {
+states: Dict[str, int] = {
     "OK": 0,
     "WARNING": 1,
     "CRITICAL": 2,
     "UNKNOWN": 3
-}  # type: Dict[str, int]
+}
 
 def report(state: str, data: str, last_check: float) -> None:
     print("%s: Last test run completed at %s\n%s" % (
diff --git a/scripts/lib/check_rabbitmq_queue.py b/scripts/lib/check_rabbitmq_queue.py
index 8bd86c007c..f5f2aa3d01 100644
--- a/scripts/lib/check_rabbitmq_queue.py
+++ b/scripts/lib/check_rabbitmq_queue.py
@@ -40,28 +40,28 @@ states = {
     3: "UNKNOWN"
 }
 
-MAX_SECONDS_TO_CLEAR_FOR_BURSTS = defaultdict(
+MAX_SECONDS_TO_CLEAR_FOR_BURSTS: DefaultDict[str, int] = defaultdict(
     lambda: 120,
     digest_emails=600,
     slow_queries=600,
-)  # type: DefaultDict[str, int]
-MAX_SECONDS_TO_CLEAR_NORMAL = defaultdict(
+)
+MAX_SECONDS_TO_CLEAR_NORMAL: DefaultDict[str, int] = defaultdict(
     lambda: 30,
     digest_emails=1200,
     slow_queries=120,
     missedmessage_mobile_notifications=120,
-)  # type: DefaultDict[str, int]
-CRITICAL_SECONDS_TO_CLEAR_FOR_BURSTS = defaultdict(
+)
+CRITICAL_SECONDS_TO_CLEAR_FOR_BURSTS: DefaultDict[str, int] = defaultdict(
     lambda: 240,
     digest_emails=1200,
     slow_queries=1200,
-)  # type: DefaultDict[str, int]
-CRITICAL_SECONDS_TO_CLEAR_NORMAL = defaultdict(
+)
+CRITICAL_SECONDS_TO_CLEAR_NORMAL: DefaultDict[str, int] = defaultdict(
     lambda: 60,
     missedmessage_mobile_notifications=180,
     digest_emails=600,
     slow_queries=600,
-)  # type: DefaultDict[str, int]
+)
 
 def analyze_queue_stats(queue_name: str, stats: Dict[str, Any],
                         queue_count_rabbitmqctl: int) -> Dict[str, Any]:
@@ -183,7 +183,7 @@ def check_rabbitmq_queues() -> None:
     queue_stats_dir = subprocess.check_output([os.path.join(ZULIP_PATH, 'scripts/get-django-setting'),
                                                'QUEUE_STATS_DIR'],
                                               universal_newlines=True).strip()
-    queue_stats = dict()  # type: Dict[str, Dict[str, Any]]
+    queue_stats: Dict[str, Dict[str, Any]] = dict()
     queues_to_check = set(normal_queues).intersection(set(queues_with_consumers))
     for queue in queues_to_check:
         fn = queue + ".stats"
diff --git a/scripts/lib/upgrade-zulip b/scripts/lib/upgrade-zulip
index 1cef7bec40..e5a823f2a7 100755
--- a/scripts/lib/upgrade-zulip
+++ b/scripts/lib/upgrade-zulip
@@ -15,7 +15,7 @@ from scripts.lib.zulip_tools import DEPLOYMENTS_DIR, FAIL, ENDC, \
     su_to_zulip, get_deployment_lock, release_deployment_lock, assert_running_as_root, \
     get_config_file, get_deploy_options
 
-config_file = get_config_file()  # type: configparser.RawConfigParser
+config_file: configparser.RawConfigParser = get_config_file()
 deploy_options = get_deploy_options(config_file)
 
 assert_running_as_root(strip_lib_from_paths=True)
diff --git a/scripts/nagios/check-rabbitmq-consumers b/scripts/nagios/check-rabbitmq-consumers
index 4a4c4e208f..79688e41cd 100755
--- a/scripts/nagios/check-rabbitmq-consumers
+++ b/scripts/nagios/check-rabbitmq-consumers
@@ -46,7 +46,7 @@ TORNADO_PROCESSES = int(get_config('application_server', 'tornado_processes', '1
 output = subprocess.check_output(['/usr/sbin/rabbitmqctl', 'list_consumers'],
                                  universal_newlines=True)
 
-consumers = defaultdict(int)  # type: Dict[str, int]
+consumers: Dict[str, int] = defaultdict(int)
 
 sys.path.append(os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(__file__)))))
 queues = set(normal_queues).union({
diff --git a/scripts/setup/generate_secrets.py b/scripts/setup/generate_secrets.py
index 68bd0e52b8..484a916ab7 100755
--- a/scripts/setup/generate_secrets.py
+++ b/scripts/setup/generate_secrets.py
@@ -52,7 +52,7 @@ def generate_secrets(development: bool = False) -> None:
         OUTPUT_SETTINGS_FILENAME = "/etc/zulip/zulip-secrets.conf"
     current_conf = get_old_conf(OUTPUT_SETTINGS_FILENAME)
 
-    lines = []  # type: List[str]
+    lines: List[str] = []
     if len(current_conf) == 0:
         lines = ['[secrets]\n']
 
diff --git a/tools/check-issue-labels b/tools/check-issue-labels
index 8d0c5fb4e6..703c28e537 100755
--- a/tools/check-issue-labels
+++ b/tools/check-issue-labels
@@ -57,7 +57,7 @@ def check_issue_labels() -> None:
                   "your api token. If you want to continue without using a token use --force.")
             sys.exit(1)
 
-    next_page_url = 'https://api.github.com/repos/zulip/zulip/issues'  # type: Optional[str]
+    next_page_url: Optional[str] = 'https://api.github.com/repos/zulip/zulip/issues'
     unlabeled_issue_urls = []
     while next_page_url:
         try:
diff --git a/tools/check-templates b/tools/check-templates
index 9d768a4986..6eb07953b4 100755
--- a/tools/check-templates
+++ b/tools/check-templates
@@ -96,7 +96,7 @@ def check_html_templates(templates: Iterable[str], all_dups: bool, fix: bool) ->
                 print(fn)
         return bad_ids_dict
 
-    bad_ids_list = []  # type: List[str]
+    bad_ids_list: List[str] = []
     archive_templates = list(filter(
         lambda fn: ('templates/zerver/archive' in fn),
         templates))
diff --git a/tools/create-test-api-docs b/tools/create-test-api-docs
index 937be8a58a..69b6c473a3 100755
--- a/tools/create-test-api-docs
+++ b/tools/create-test-api-docs
@@ -109,7 +109,7 @@ def create_user_docs() -> None:
         for line in open(fn):
             calls.append(ujson.loads(line))
 
-        pattern_dict = defaultdict(list)  # type: Dict[str, List[Call]]
+        pattern_dict: Dict[str, List[Call]] = defaultdict(list)
         for call in calls:
             if 'pattern' in call:
                 pattern = clean_up_pattern(call['pattern'])
@@ -124,7 +124,7 @@ def create_user_docs() -> None:
             ('json', 'legacy'),
         ]
 
-        groups = dict()  # type: Dict[str, Set[str]]
+        groups: Dict[str, Set[str]] = dict()
         for prefix, name in tups:
             groups[name] = {p for p in patterns if p.startswith(prefix)}
             patterns -= groups[name]
diff --git a/tools/documentation_crawler/documentation_crawler/spiders/check_help_documentation.py b/tools/documentation_crawler/documentation_crawler/spiders/check_help_documentation.py
index bd4b96c7fb..c831fa095e 100644
--- a/tools/documentation_crawler/documentation_crawler/spiders/check_help_documentation.py
+++ b/tools/documentation_crawler/documentation_crawler/spiders/check_help_documentation.py
@@ -20,8 +20,8 @@ class UnusedImagesLinterSpider(BaseDocumentationSpider):
 
     def __init__(self, *args: Any, **kwargs: Any) -> None:
         super().__init__(*args, **kwargs)
-        self.static_images = set()  # type: Set[str]
-        self.images_static_dir = get_images_dir(self.images_path)  # type: str
+        self.static_images: Set[str] = set()
+        self.images_static_dir: str = get_images_dir(self.images_path)
 
     def _is_external_url(self, url: str) -> bool:
         is_external = url.startswith('http') and self.start_urls[0] not in url
@@ -43,7 +43,7 @@ class UnusedImagesLinterSpider(BaseDocumentationSpider):
 class HelpDocumentationSpider(UnusedImagesLinterSpider):
     name = "help_documentation_crawler"
     start_urls = ['http://localhost:9981/help']
-    deny_domains = []  # type: List[str]
+    deny_domains: List[str] = []
     deny = ['/privacy']
     images_path = "static/images/help"
 
@@ -51,7 +51,7 @@ class HelpDocumentationSpider(UnusedImagesLinterSpider):
 class APIDocumentationSpider(UnusedImagesLinterSpider):
     name = 'api_documentation_crawler'
     start_urls = ['http://localhost:9981/api']
-    deny_domains = []  # type: List[str]
+    deny_domains: List[str] = []
     images_path = "static/images/api"
 
 class PorticoDocumentationSpider(BaseDocumentationSpider):
@@ -79,4 +79,4 @@ class PorticoDocumentationSpider(BaseDocumentationSpider):
                   'http://localhost:9981/for/working-groups-and-communities',
                   'http://localhost:9981/for/mystery-hunt',
                   'http://localhost:9981/security']
-    deny_domains = []  # type: List[str]
+    deny_domains: List[str] = []
diff --git a/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py b/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py
index aac2225162..4108dbeeb0 100644
--- a/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py
+++ b/tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py
@@ -44,12 +44,12 @@ VNU_IGNORE = re.compile(r'|'.join([
 
 
 class BaseDocumentationSpider(scrapy.Spider):
-    name = None  # type: Optional[str]
+    name: Optional[str] = None
     # Exclude domain address.
-    deny_domains = []  # type: List[str]
-    start_urls = []  # type: List[str]
-    deny = []  # type: List[str]
-    file_extensions = ['.' + ext for ext in IGNORED_EXTENSIONS]  # type: List[str]
+    deny_domains: List[str] = []
+    start_urls: List[str] = []
+    deny: List[str] = []
+    file_extensions: List[str] = ['.' + ext for ext in IGNORED_EXTENSIONS]
     tags = ('a', 'area', 'img')
     attrs = ('href', 'src')
 
@@ -107,7 +107,7 @@ class BaseDocumentationSpider(scrapy.Spider):
         return callback
 
     def _make_requests(self, url: str) -> Iterable[Request]:
-        callback = self.parse  # type: Callable[[Response], Optional[Iterable[Request]]]
+        callback: Callable[[Response], Optional[Iterable[Request]]] = self.parse
         dont_filter = False
         method = 'GET'
         if self._is_external_url(url):
diff --git a/tools/fetch-contributor-data b/tools/fetch-contributor-data
index 7fcb6e59a4..03eac9c832 100755
--- a/tools/fetch-contributor-data
+++ b/tools/fetch-contributor-data
@@ -44,7 +44,7 @@ ContributorsJSON = TypedDict('ContributorsJSON', {
 logger = logging.getLogger('zulip.fetch_contributors_json')
 
 def fetch_contributors(repo_link: str) -> Optional[List[Dict[str, Dict[str, Any]]]]:
-    r = requests.get(repo_link, verify=os.environ.get('CUSTOM_CA_CERTIFICATES'))  # type: requests.Response
+    r: requests.Response = requests.get(repo_link, verify=os.environ.get('CUSTOM_CA_CERTIFICATES'))
     return r.json() if r.status_code == 200 else None
 
 def write_to_disk(json_data: ContributorsJSON, out_file: str) -> None:
@@ -77,8 +77,8 @@ def update_contributor_data_file() -> None:
         'zulip-android': 'https://api.github.com/repos/zulip/zulip-android/stats/contributors',
     }
 
-    data = dict(date=str(date.today()), contrib=[])  # type: ContributorsJSON
-    contribs_list = {}  # type: Dict[str, Dict[str, Union[str, int]]]
+    data: ContributorsJSON = dict(date=str(date.today()), contrib=[])
+    contribs_list: Dict[str, Dict[str, Union[str, int]]] = {}
     retry_attempts = 0
 
     while True:
diff --git a/tools/i18n/process-mobile-i18n b/tools/i18n/process-mobile-i18n
index a9b5d679ae..d4764f2ae7 100755
--- a/tools/i18n/process-mobile-i18n
+++ b/tools/i18n/process-mobile-i18n
@@ -28,7 +28,7 @@ def get_translation_stats(resource_path: str) -> Dict[str, int]:
     not_translated = len([i for i in raw_info.items() if i[1] == ''])
     return {'total': total, 'not_translated': not_translated}
 
-translation_stats = {}  # type: Dict[str, Dict[str, int]]
+translation_stats: Dict[str, Dict[str, int]] = {}
 locale_paths = []  # List[str]
 for locale in get_locales():
     path = get_json_filename(locale)
diff --git a/tools/lib/html_branches.py b/tools/lib/html_branches.py
index fe6f616b40..78f8205cc5 100644
--- a/tools/lib/html_branches.py
+++ b/tools/lib/html_branches.py
@@ -26,7 +26,7 @@ class HtmlTreeBranch:
         self.fn = fn
         self.line = tags[-1].token.line
 
-        self.words = set()  # type: Set[str]
+        self.words: Set[str] = set()
         for tag in tags:
             for word in tag.words:
                 self.words.add(word)
@@ -60,8 +60,8 @@ class Node:
     def __init__(self, token: Token, parent: "Optional[Node]") -> None:
         # FIXME parent parameter is not used!
         self.token = token
-        self.children = []  # type: List[Node]
-        self.parent = None  # type: Optional[Node]
+        self.children: List[Node] = []
+        self.parent: Optional[Node] = None
 
 
 class TagInfo:
@@ -87,8 +87,8 @@ class TagInfo:
 def get_tag_info(token: Token) -> TagInfo:
     s = token.s
     tag = token.tag
-    classes = []  # type: List[str]
-    ids = []  # type: List[str]
+    classes: List[str] = []
+    ids: List[str] = []
 
     searches = [
         (classes, ' class="(.*?)"'),
@@ -111,7 +111,7 @@ def split_for_id_and_class(element: str) -> List[str]:
     # attributes from HTML tags. This also takes care of template variables
     # in string during splitting process. For eg. 'red black {{ a|b|c }}'
     # is split as ['red', 'black', '{{ a|b|c }}']
-    outside_braces = True  # type: bool
+    outside_braces: bool = True
     lst = []
     s = ''
 
@@ -134,7 +134,7 @@ def split_for_id_and_class(element: str) -> List[str]:
 
 def html_branches(text: str, fn: Optional[str] = None) -> List[HtmlTreeBranch]:
     tree = html_tag_tree(text)
-    branches = []  # type: List[HtmlTreeBranch]
+    branches: List[HtmlTreeBranch] = []
 
     def walk(node: Node, tag_info_list: Optional[List[TagInfo]] = None) -> None:
         info = get_tag_info(node.token)
@@ -179,7 +179,7 @@ def html_tag_tree(text: str) -> Node:
 
 
 def build_id_dict(templates: List[str]) -> (Dict[str, List[str]]):
-    template_id_dict = defaultdict(list)  # type: (Dict[str, List[str]])
+    template_id_dict: (Dict[str, List[str]]) = defaultdict(list)
 
     for fn in templates:
         with open(fn) as f:
diff --git a/tools/lib/pretty_print.py b/tools/lib/pretty_print.py
index 8b6787a239..2e03597206 100644
--- a/tools/lib/pretty_print.py
+++ b/tools/lib/pretty_print.py
@@ -17,23 +17,24 @@ def pretty_print_html(html: str, num_spaces: int = 4) -> str:
     # We will keep a stack of "start" tags so that we know
     # when HTML ranges end.  Note that some start tags won't
     # be blocks from an indentation standpoint.
-    stack = []  # type: List[Dict[str, Any]]
+    stack: List[Dict[str, Any]] = []
 
     # Seed our stack with a pseudo entry to make depth calculations
     # easier.
-    info = dict(
+    info: Dict[str, Any] = dict(
         block=False,
         depth=-1,
         line=-1,
         token_kind='html_start',
         tag='html',
         extra_indent=0,
-        ignore_lines=[])  # type: Dict[str, Any]
+        ignore_lines=[],
+    )
     stack.append(info)
 
     # Our main job is to figure out offsets that we use to nudge lines
     # over by.
-    offsets = {}  # type: Dict[int, int]
+    offsets: Dict[int, int] = {}
 
     # Loop through our start/end tokens, and calculate offsets.  As
     # we proceed, we will push/pop info dictionaries on/off a stack.
diff --git a/tools/linter_lib/custom_check.py b/tools/linter_lib/custom_check.py
index 8a3a4453d6..aa07c6708d 100644
--- a/tools/linter_lib/custom_check.py
+++ b/tools/linter_lib/custom_check.py
@@ -51,7 +51,7 @@ FILES_WITH_LEGACY_SUBJECT = {
     'zerver/tests/test_narrow.py',
 }
 
-shebang_rules = [
+shebang_rules: List["Rule"] = [
     {'pattern': '^#!',
      'description': "zerver library code shouldn't have a shebang line.",
      'include_only': {'zerver/'}},
@@ -63,14 +63,14 @@ shebang_rules = [
      " for interpreters other than sh."},
     {'pattern': '^#!/usr/bin/env python$',
      'description': "Use `#!/usr/bin/env python3` instead of `#!/usr/bin/env python`."}
-]  # type: List[Rule]
+]
 
-trailing_whitespace_rule = {
+trailing_whitespace_rule: "Rule" = {
     'pattern': r'\s+$',
     'strip': '\n',
     'description': 'Fix trailing whitespace'
-}  # type: Rule
-whitespace_rules = [
+}
+whitespace_rules: List["Rule"] = [
     # This linter should be first since bash_rules depends on it.
     trailing_whitespace_rule,
     {'pattern': 'http://zulip.readthedocs.io',
@@ -80,14 +80,14 @@ whitespace_rules = [
      'strip': '\n',
      'exclude': {'tools/ci/success-http-headers.txt'},
      'description': 'Fix tab-based whitespace'},
-]  # type: List[Rule]
-comma_whitespace_rule = [
+]
+comma_whitespace_rule: List["Rule"] = [
     {'pattern': ', {2,}[^#/ ]',
      'exclude': {'zerver/tests', 'frontend_tests/node_tests', 'corporate/tests'},
      'description': "Remove multiple whitespaces after ','",
      'good_lines': ['foo(1, 2, 3)', 'foo = bar  # some inline comment'],
      'bad_lines': ['foo(1,  2, 3)', 'foo(1,    2, 3)']},
-]  # type: List[Rule]
+]
 markdown_whitespace_rules = list([rule for rule in whitespace_rules if rule['pattern'] != r'\s+$']) + [
     # Two spaces trailing a line with other content is okay--it's a markdown line break.
     # This rule finds one space trailing a non-space, three or more trailing spaces, and
@@ -560,7 +560,7 @@ css_rules = RuleList(
     ],
 )
 
-prose_style_rules = [
+prose_style_rules: List["Rule"] = [
     {'pattern': r'[^\/\#\-"]([jJ]avascript)',  # exclude usage in hrefs/divs
      'exclude': {"docs/documentation/api.md"},
      'description': "javascript should be spelled JavaScript"},
@@ -576,8 +576,8 @@ prose_style_rules = [
     {'pattern': '[^-_p]botserver(?!rc)|bot server',
      'description': "Use Botserver instead of botserver or bot server."},
     *comma_whitespace_rule,
-]  # type: List[Rule]
-html_rules = whitespace_rules + prose_style_rules + [
+]
+html_rules: List["Rule"] = whitespace_rules + prose_style_rules + [
     {'pattern': 'subject|SUBJECT',
      'exclude': {'templates/zerver/email.html'},
      'exclude_pattern': 'email subject',
@@ -703,7 +703,7 @@ html_rules = whitespace_rules + prose_style_rules + [
      },
      'good_lines': ['#my-style {color: blue;}', 'style="display: none"', "style='display: none"],
      'bad_lines': ['<p style="color: blue;">Foo</p>', 'style = "color: blue;"']},
-]  # type: List[Rule]
+]
 
 handlebars_rules = RuleList(
     langs=['hbs'],
diff --git a/tools/renumber-migrations b/tools/renumber-migrations
index 1539fd2988..10998a8da7 100755
--- a/tools/renumber-migrations
+++ b/tools/renumber-migrations
@@ -19,7 +19,7 @@ def validate_order(order: List[int], length: int) -> None:
             sys.exit(1)
 
 def renumber_migration(conflicts: List[str], order: List[int], last_correct_migration: str) -> None:
-    stack = []  # type: List[str]
+    stack: List[str] = []
     for i in order:
         if conflicts[i-1][0:4] not in stack:
             stack.append(conflicts[i-1][0:4])
@@ -53,8 +53,8 @@ def resolve_conflicts(conflicts: List[str], files_list: List[str]) -> None:
 if __name__ == '__main__':
 
     while True:
-        conflicts = []  # type: List[str]
-        stack = []  # type: List[str]
+        conflicts: List[str] = []
+        stack: List[str] = []
         files_list = [os.path.basename(path) for path in glob.glob("zerver/migrations/????_*.py")]
         file_index = [file[0:4] for file in files_list]
 
diff --git a/tools/run-dev.py b/tools/run-dev.py
index e2d695c2af..dce34c155d 100755
--- a/tools/run-dev.py
+++ b/tools/run-dev.py
@@ -84,7 +84,7 @@ if options.interface is None:
 elif options.interface == "":
     options.interface = None
 
-runserver_args = []  # type: List[str]
+runserver_args: List[str] = []
 base_port = 9991
 if options.test:
     base_port = 9981
@@ -199,9 +199,9 @@ def fetch_request(url: str, callback: Any, **kwargs: Any) -> "Generator[Callable
 
 class BaseHandler(web.RequestHandler):
     # target server ip
-    target_host = '127.0.0.1'  # type: str
+    target_host: str = '127.0.0.1'
     # target server port
-    target_port = None  # type: int
+    target_port: int
 
     def _add_request_headers(
         self, exclude_lower_headers_list: Optional[List[str]] = None
diff --git a/tools/run-mypy b/tools/run-mypy
index c1ecdfac2d..939b667616 100755
--- a/tools/run-mypy
+++ b/tools/run-mypy
@@ -69,7 +69,7 @@ if not python_files and not pyi_files:
     print("There are no files to run mypy on.")
     sys.exit(0)
 
-mypy_args = []  # type: List[str]
+mypy_args: List[str] = []
 if args.quiet:
     mypy_args += ["--no-error-summary"]
 mypy_args += ["--"] + python_files + pyi_files
diff --git a/tools/setup/emoji/emoji_names.py b/tools/setup/emoji/emoji_names.py
index d297244f76..37f7419db2 100644
--- a/tools/setup/emoji/emoji_names.py
+++ b/tools/setup/emoji/emoji_names.py
@@ -1,6 +1,6 @@
 from typing import Any, Dict
 
-EMOJI_NAME_MAPS = {
+EMOJI_NAME_MAPS: Dict[str, Dict[str, Any]] = {
     # seems like best emoji for happy
     '1f600': {'canonical_name': 'grinning', 'aliases': ['happy']},
     '1f603': {'canonical_name': 'smiley', 'aliases': []},
@@ -1528,4 +1528,4 @@ EMOJI_NAME_MAPS = {
     '1f6a9': {'canonical_name': 'triangular_flag', 'aliases': []},
     # solidarity from iemoji
     '1f38c': {'canonical_name': 'crossed_flags', 'aliases': ['solidarity']},
-}   # type: Dict[str, Dict[str, Any]]
+}
diff --git a/tools/setup/emoji/emoji_setup_utils.py b/tools/setup/emoji/emoji_setup_utils.py
index ccc39b9471..64bdfbdb9e 100644
--- a/tools/setup/emoji/emoji_setup_utils.py
+++ b/tools/setup/emoji/emoji_setup_utils.py
@@ -47,7 +47,7 @@ EMOTICON_CONVERSIONS = {
 }
 
 def emoji_names_for_picker(emoji_name_maps: Dict[str, Dict[str, Any]]) -> List[str]:
-    emoji_names = []  # type: List[str]
+    emoji_names: List[str] = []
     for emoji_code, name_info in emoji_name_maps.items():
         emoji_names.append(name_info["canonical_name"])
         emoji_names.extend(name_info["aliases"])
@@ -73,8 +73,8 @@ def get_emoji_code(emoji_dict: Dict[str, Any]) -> str:
 # `emoji_data`.
 def generate_emoji_catalog(emoji_data: List[Dict[str, Any]],
                            emoji_name_maps: Dict[str, Dict[str, Any]]) -> Dict[str, List[str]]:
-    sort_order = {}  # type: Dict[str, int]
-    emoji_catalog = defaultdict(list)  # type: Dict[str, List[str]]
+    sort_order: Dict[str, int] = {}
+    emoji_catalog: Dict[str, List[str]] = defaultdict(list)
 
     for emoji_dict in emoji_data:
         emoji_code = get_emoji_code(emoji_dict)
@@ -100,7 +100,7 @@ def emoji_is_universal(emoji_dict: Dict[str, Any]) -> bool:
     return True
 
 def generate_codepoint_to_name_map(emoji_name_maps: Dict[str, Dict[str, Any]]) -> Dict[str, str]:
-    codepoint_to_name = {}  # type: Dict[str, str]
+    codepoint_to_name: Dict[str, str] = {}
     for emoji_code, name_info in emoji_name_maps.items():
         codepoint_to_name[emoji_code] = name_info["canonical_name"]
     return codepoint_to_name
diff --git a/tools/setup/emoji/export_emoji_names_to_csv b/tools/setup/emoji/export_emoji_names_to_csv
index db90880e2d..d7d8717e9a 100755
--- a/tools/setup/emoji/export_emoji_names_to_csv
+++ b/tools/setup/emoji/export_emoji_names_to_csv
@@ -21,7 +21,7 @@ ZULIP_PATH = os.path.dirname(TOOLS_DIR_PATH)
 # `emoji.json` file is same in all four emoji-datasource packages.
 EMOJI_DATA_PATH = os.path.join(ZULIP_PATH, 'node_modules', 'emoji-datasource-google', 'emoji.json')
 
-sorting_info = {}   # type: Dict[str, Any]
+sorting_info: Dict[str, Any] = {}
 column_names = [
     'Codepoint',
     'New sorting info',
@@ -47,7 +47,7 @@ name_entry_regex = re.compile(r"'(?P<emoji_code>[a-z0-9-]+)': "
 explanation_regex = re.compile(r"    # (?P<explanation_line>[^\r\n\t]+)")
 
 def prepare_sorting_info() -> None:
-    emoji_data = []     # type: List[Dict[str, Any]]
+    emoji_data: List[Dict[str, Any]] = []
     with open(EMOJI_DATA_PATH) as fp:
         emoji_data = ujson.load(fp)
 
@@ -90,7 +90,7 @@ def main() -> None:
     args = parser.parse_args()
     prepare_sorting_info()
     output_data = [column_names, ]
-    explanation_lines = []  # type: List[str]
+    explanation_lines: List[str] = []
     with open(args.input_file_path) as fp:
         for line in fp.readlines():
             match = name_entry_regex.search(line)
diff --git a/tools/setup/emoji/generate_emoji_names_table b/tools/setup/emoji/generate_emoji_names_table
index 3493ecff65..77a21ed39b 100755
--- a/tools/setup/emoji/generate_emoji_names_table
+++ b/tools/setup/emoji/generate_emoji_names_table
@@ -119,14 +119,14 @@ SORTED_CATEGORIES = [
     'Skin Tones',
 ]
 
-emoji_code_to_zulip_names = {}      # type: Dict[str, str]
-emoji_code_to_iamcal_names = {}     # type: Dict[str, str]
-emoji_code_to_gemoji_names = {}     # type: Dict[str, str]
-emoji_collection = {category: [] for category in SORTED_CATEGORIES}     # type: Dict[str, List[Dict[str, Any]]]
+emoji_code_to_zulip_names: Dict[str, str] = {}
+emoji_code_to_iamcal_names: Dict[str, str] = {}
+emoji_code_to_gemoji_names: Dict[str, str] = {}
+emoji_collection: Dict[str, List[Dict[str, Any]]] = {category: [] for category in SORTED_CATEGORIES}
 
 def generate_emoji_code_to_emoji_names_maps() -> None:
     # Prepare gemoji names map.
-    reverse_unified_reactions_map = {}  # type: Dict[str, List[str]]
+    reverse_unified_reactions_map: Dict[str, List[str]] = {}
     for name in UNIFIED_REACTIONS_MAP:
         emoji_code = UNIFIED_REACTIONS_MAP[name]
         if emoji_code in reverse_unified_reactions_map:
diff --git a/tools/setup/emoji/import_emoji_names_from_csv b/tools/setup/emoji/import_emoji_names_from_csv
index dfe1af9b5b..b0c13d6f80 100755
--- a/tools/setup/emoji/import_emoji_names_from_csv
+++ b/tools/setup/emoji/import_emoji_names_from_csv
@@ -35,10 +35,10 @@ FILE_TEMPLATE = (
     "}   # type: Dict[str, Dict[str, Any]]\n"
 )
 
-emoji_names = set()     # type: Set[str]
+emoji_names: Set[str] = set()
 
 def load_data(data_file: str) -> List[List[str]]:
-    emoji_name_data = []    # type: List[List[str]]
+    emoji_name_data: List[List[str]] = []
     with open(data_file, newline='') as fp:
         data = csv.reader(fp)
         for row in data:
@@ -66,13 +66,13 @@ def prepare_explanation(explanation: str) -> str:
     if explanation == '':
         return ''
 
-    wrapper_config = {
+    wrapper_config: Dict[str, Any] = {
         'width': 80,
         'break_long_words': False,
         'break_on_hyphens': False,
         'initial_indent': '\n    # ',
         'subsequent_indent': '\n    # ',
-    }   # type: Dict[str, Any]
+    }
     wrapped_lines = textwrap.wrap(explanation.strip(), **wrapper_config)
     return ''.join(wrapped_lines)