diff --git a/src/dotenv/main.py b/src/dotenv/main.py
index 43248819..e7b8392a 100644
--- a/src/dotenv/main.py
+++ b/src/dotenv/main.py
@@ -25,23 +25,23 @@ def with_warn_for_invalid_lines(mappings: Iterator[Binding]) -> Iterator[Binding
         yield mapping
 
 
-class DotEnv():
+class DotEnv:
     def __init__(
         self,
         dotenv_path: Optional[Union[str, os.PathLike]],
         stream: Optional[IO[str]] = None,
         verbose: bool = False,
-        encoding: Union[None, str] = None,
+        encoding: Optional[str] = None,
         interpolate: bool = True,
         override: bool = True,
     ) -> None:
-        self.dotenv_path = dotenv_path  # type: Optional[Union[str, os.PathLike]]
-        self.stream = stream  # type: Optional[IO[str]]
-        self._dict = None  # type: Optional[Dict[str, Optional[str]]]
-        self.verbose = verbose  # type: bool
-        self.encoding = encoding  # type: Union[None, str]
-        self.interpolate = interpolate  # type: bool
-        self.override = override  # type: bool
+        self.dotenv_path: Optional[Union[str, os.PathLike]] = dotenv_path
+        self.stream: Optional[IO[str]] = stream
+        self._dict: Optional[Dict[str, Optional[str]]] = None
+        self.verbose: bool = verbose
+        self.encoding: Optional[str] = encoding
+        self.interpolate: bool = interpolate
+        self.override: bool = override
 
     @contextmanager
     def _get_stream(self) -> Iterator[IO[str]]:
@@ -153,7 +153,7 @@ def set_key(
     an orphan .env somewhere in the filesystem
     """
     if quote_mode not in ("always", "auto", "never"):
-        raise ValueError("Unknown quote_mode: {}".format(quote_mode))
+        raise ValueError(f"Unknown quote_mode: {quote_mode}")
 
     quote = (
         quote_mode == "always"
@@ -165,9 +165,9 @@ def set_key(
     else:
         value_out = value_to_set
     if export:
-        line_out = 'export {}={}\n'.format(key_to_set, value_out)
+        line_out = f'export {key_to_set}={value_out}\n'
     else:
-        line_out = "{}={}\n".format(key_to_set, value_out)
+        line_out = f"{key_to_set}={value_out}\n"
 
     with rewrite(dotenv_path, encoding=encoding) as (source, dest):
         replaced = False
@@ -222,14 +222,14 @@ def resolve_variables(
     values: Iterable[Tuple[str, Optional[str]]],
     override: bool,
 ) -> Mapping[str, Optional[str]]:
-    new_values = {}  # type: Dict[str, Optional[str]]
+    new_values: Dict[str, Optional[str]] = {}
 
     for (name, value) in values:
         if value is None:
             result = None
         else:
             atoms = parse_variables(value)
-            env = {}  # type: Dict[str, Optional[str]]
+            env: Dict[str, Optional[str]] = {}
             if override:
                 env.update(os.environ)  # type: ignore
                 env.update(new_values)
diff --git a/src/dotenv/parser.py b/src/dotenv/parser.py
index 398bd49a..735f14a3 100644
--- a/src/dotenv/parser.py
+++ b/src/dotenv/parser.py
@@ -25,23 +25,16 @@ def make_regex(string: str, extra_flags: int = 0) -> Pattern[str]:
 _single_quote_escapes = make_regex(r"\\[\\']")
 
 
-Original = NamedTuple(
-    "Original",
-    [
-        ("string", str),
-        ("line", int),
-    ],
-)
-
-Binding = NamedTuple(
-    "Binding",
-    [
-        ("key", Optional[str]),
-        ("value", Optional[str]),
-        ("original", Original),
-        ("error", bool),
-    ],
-)
+class Original(NamedTuple):
+    string: str
+    line: int
+
+
+class Binding(NamedTuple):
+    key: Optional[str]
+    value: Optional[str]
+    original: Original
+    error: bool
 
 
 class Position:
@@ -155,7 +148,7 @@ def parse_binding(reader: Reader) -> Binding:
         reader.read_regex(_whitespace)
         if reader.peek(1) == "=":
             reader.read_regex(_equal_sign)
-            value = parse_value(reader)  # type: Optional[str]
+            value: Optional[str] = parse_value(reader)
         else:
             value = None
         reader.read_regex(_comment)