appium
diff --git a/‎.gitignore
+3 b/‎.gitignore
+3
diff --git a/‎.pre-commit-config.yaml
+6 b/‎.pre-commit-config.yaml
+6
diff --git a/‎.travis.yml
+1-5 b/‎.travis.yml
+1-5
diff --git a/‎Pipfile
+7-6 b/‎Pipfile
+7-6
diff --git a/‎README.md
+6-2 b/‎README.md
+6-2
diff --git a/‎appium/common/helper.py
+6-25 b/‎appium/common/helper.py
+6-25
diff --git a/‎appium/common/logger.py
+1-1 b/‎appium/common/logger.py
+1-1
diff --git a/‎appium/saucetestcase.py
+7-6 b/‎appium/saucetestcase.py
+7-6
diff --git a/‎appium/webdriver/appium_connection.py
+5-1 b/‎appium/webdriver/appium_connection.py
+5-1
@@ -5,6 +5,7 @@
 *._*
 *.log
 *.log.*
+_*/
 
 *.pyc
 *.egg-info
@@ -14,10 +15,12 @@ MANIFEST
 build
 dist
 
+# Cache
 .cache
 __pycache__
 .idea
 .pytest_cache
+.mypy_cache
 
 # Virtual Environments
 venv*
 
@@ -8,3 +8,9 @@
     hooks:
     -   id: isort
         args: ["-rc", "."]
+-   repo: https://github.com/pre-commit/mirrors-mypy
+    rev: 'v0.761'
+    hooks:
+    -   id: mypy
+        entry: mypy appium/ test/
+        pass_filenames: false
@@ -2,12 +2,8 @@ language: python
 dist: xenial
 
 python:
-  - "2.7"
-  - "3.4"
-  - "3.5"
-  - "3.6"
   - "3.7"
-#  - "3.8-dev"  # TODO Remove comment-out when pylint and astroid upgraded to the latest and py2 support dropped
+  - "3.8"
 
 install:
   - pip install tox-travis
 
@@ -4,24 +4,25 @@ url = "https://pypi.org/simple"
 verify_ssl = true
 
 [dev-packages]
-pre-commit = "~=1.13"
+pre-commit = "~=2.1"
 
 [packages]
 selenium = "~=3.141"
 
 autopep8 = "~=1.5"
 
-pytest = "~=4.0"
+pytest = "~=5.3"
 pytest-cov = "~=2.8"
 
 tox = "~=3.14"
 tox-travis = "~=0.12"
 
 httpretty = "~=0.9"
 python-dateutil = "~=2.8"
-mock = "~=3.0"
+mock = "~=4.0"
 
-# TODO Update to the latest ver when py2 support dropped
-pylint = "~=1.9"
-astroid = "~=1.6"
+pylint = "~=2.4"
+astroid = "~=2.3"
 isort = "~=4.3"
+
+mypy = "==0.761"
@@ -49,14 +49,18 @@ download and unarchive the source tarball (Appium-Python-Client-X.X.tar.gz).
 
 - Style Guide: https://www.python.org/dev/peps/pep-0008/
     - `autopep8` helps to format code automatically
-        ```
+        ```shell
         $ python -m autopep8 -r --global-config .config-pep8 -i .
         ```
     - `isort` helps to order imports automatically
-        ```
+        ```shell
         $ python -m isort -rc .
         ```
         - When you use newly 3rd party modules, add it to [.isort.cfg](.isort.cfg) to keep import order correct
+    - `mypy` helps to check explicit type declarations
+        ```shell
+        $ python -m mypy appium
+        ```
 - Docstring style: Google Style
     - Refer [link](https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html)
 - You can customise `CHANGELOG.rst` with commit messages following [.gitchangelog.rc](.gitchangelog.rc)
 
@@ -12,44 +12,25 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from collections import OrderedDict
+from typing import Any, Dict
 
 from appium import version as appium_version
 
 
-def appium_bytes(value, encoding):
-    """Return a bytes-like object
-
-    Has _appium_ prefix to avoid overriding built-in bytes.
-
-    Args:
-        value (str): A value to convert
-        encoding (str): A encoding which will convert to
-
-    Returns:
-        str: A bytes-like object
-    """
-
-    try:
-        return bytes(value, encoding)  # Python 3
-    except TypeError:
-        return value  # Python 2
-
-
-def extract_const_attributes(cls):
+def extract_const_attributes(cls: type) -> Dict[str, Any]:
     """Return dict with constants attributes and values in the class(e.g. {'VAL1': 1, 'VAL2': 2})
 
     Args:
         cls (type): Class to be extracted constants
 
     Returns:
-        OrderedDict: dict with constants attributes and values in the class
+        dict: dict with constants attributes and values in the class
     """
-    return OrderedDict(
-        [(attr, value) for attr, value in vars(cls).items() if not callable(getattr(cls, attr)) and attr.isupper()])
+    return dict([(attr, value) for attr, value in vars(cls).items()
+                 if not callable(getattr(cls, attr)) and attr.isupper()])
 
 
-def library_version():
+def library_version() -> str:
     """Return a version of this python library
     """
 
 
@@ -16,7 +16,7 @@
 import sys
 
 
-def setup_logger(level=logging.NOTSET):
+def setup_logger(level: int = logging.NOTSET) -> None:
     logger.propagate = False
     logger.setLevel(level)
     handler = logging.StreamHandler(stream=sys.stderr)
 
@@ -19,6 +19,7 @@
 import os
 import sys
 import unittest
+from typing import Callable, List
 
 from sauceclient import SauceClient
 
@@ -29,8 +30,8 @@
 sauce = SauceClient(SAUCE_USERNAME, SAUCE_ACCESS_KEY)
 
 
-def on_platforms(platforms):
-    def decorator(base_class):
+def on_platforms(platforms: List[str]) -> Callable[[type], None]:
+    def decorator(base_class: type) -> None:
         module = sys.modules[base_class.__module__].__dict__
         for i, platform in enumerate(platforms):
             name = "%s_%s" % (base_class.__name__, i + 1)
@@ -40,16 +41,16 @@ def decorator(base_class):
 
 
 class SauceTestCase(unittest.TestCase):
-    def setUp(self):
-        self.desired_capabilities['name'] = self.id()
+    def setUp(self) -> None:
+        self.desired_capabilities['name'] = self.id()  # type: ignore
         sauce_url = "http://%s:%[email protected]:80/wd/hub"
         self.driver = webdriver.Remote(
-            desired_capabilities=self.desired_capabilities,
+            desired_capabilities=self.desired_capabilities,  # type: ignore
             command_executor=sauce_url % (SAUCE_USERNAME, SAUCE_ACCESS_KEY)
         )
         self.driver.implicitly_wait(30)
 
-    def tearDown(self):
+    def tearDown(self) -> None:
         print("Link to your job: https://saucelabs.com/jobs/%s" % self.driver.session_id)
         try:
             if sys.exc_info() == (None, None, None):
 
@@ -13,16 +13,20 @@
 # limitations under the License.
 
 import uuid
+from typing import TYPE_CHECKING, Any, Dict
 
 from selenium.webdriver.remote.remote_connection import RemoteConnection
 
 from appium.common.helper import library_version
 
+if TYPE_CHECKING:
+    from urllib.parse import ParseResult
+
 
 class AppiumConnection(RemoteConnection):
 
     @classmethod
-    def get_remote_connection_headers(cls, parsed_url, keep_alive=True):
+    def get_remote_connection_headers(cls, parsed_url: 'ParseResult', keep_alive: bool = True) -> Dict[str, Any]:
         """Override get_remote_connection_headers in RemoteConnection"""
         headers = RemoteConnection.get_remote_connection_headers(parsed_url, keep_alive=keep_alive)
         headers['User-Agent'] = 'appium/python {} ({})'.format(library_version(), headers['User-Agent'])