refactor: prefer f-strings to .format in docs

docs/source/cheat_sheet_py3.rst

@@ -276,7 +276,7 @@ See :ref:`async-and-await` for the full detail on typing coroutines and asynchro
    # A coroutine is typed like a normal function
    async def countdown35(tag: str, count: int) -> str:
        while count > 0:
-           print('T-minus {} ({})'.format(count, tag))
+           print(f'T-minus {count} ({tag})')
            await asyncio.sleep(0.1)
            count -= 1
        return "Blastoff!"

docs/source/final_attrs.rst

@@ -33,7 +33,7 @@ further assignments to final names in type-checked code:
 
    from typing import Final
 
-   RATE: Final = 3000
+   RATE: Final = 3_000
 
    class Base:
        DEFAULT_ID: Final = 0

docs/source/generics.rst

@@ -159,7 +159,7 @@ non-generic. For example:
 
    class StrDict(dict[str, str]):  # This is a non-generic subclass of dict
        def __str__(self) -> str:
-           return 'StrDict({})'.format(super().__str__())
+           return f'StrDict({super().__str__()})'
 
    data: StrDict[int, int]  # Error! StrDict is not generic
    data2: StrDict  # OK

docs/source/getting_started.rst

@@ -129,7 +129,7 @@ Arguments with default values can be annotated like so:
 .. code-block:: python
 
    def greeting(name: str, excited: bool = False) -> str:
-       message = 'Hello, {}'.format(name)
+       message = f'Hello, {name}'
        if excited:
            message += '!!!'
        return message
@@ -213,7 +213,7 @@ ints or strings, but no other types. You can express this using the :py:data:`~t
 
    def normalize_id(user_id: Union[int, str]) -> str:
        if isinstance(user_id, int):
-           return 'user-{}'.format(100000 + user_id)
+           return f'user-{100_000 + user_id}'
        else:
            return user_id
 

docs/source/kinds_of_types.rst

@@ -452,7 +452,7 @@ but it's not obvious from its signature:
 
     def greeting(name: str) -> str:
         if name:
-            return 'Hello, {}'.format(name)
+            return f'Hello, {name}'
         else:
             return 'Hello, stranger'
 
@@ -469,7 +469,7 @@ enabled:
 
     def greeting(name: Optional[str]) -> str:
         if name:
-            return 'Hello, {}'.format(name)
+            return f'Hello, {name}'
         else:
             return 'Hello, stranger'
 

docs/source/literal_types.rst

@@ -446,7 +446,7 @@ Let's start with a definition:
 
   def assert_never(value: NoReturn) -> NoReturn:
       # This also works in runtime as well:
-      assert False, 'This code should never be reached, got: {0}'.format(value)
+      assert False, f'This code should never be reached, got: {value}'
 
   class Direction(Enum):
       up = 'up'

docs/source/more_types.rst

@@ -840,7 +840,7 @@ expect to get back when ``await``-ing the coroutine.
    import asyncio
 
    async def format_string(tag: str, count: int) -> str:
-       return 'T-minus {} ({})'.format(count, tag)
+       return f'T-minus {count} ({tag})'
 
    async def countdown_1(tag: str, count: int) -> str:
        while count > 0:
@@ -882,7 +882,7 @@ You may also choose to create a subclass of :py:class:`~typing.Awaitable` instea
 
        def __await__(self) -> Generator[Any, None, str]:
            for i in range(n, 0, -1):
-               print('T-minus {} ({})'.format(i, tag))
+               print(f'T-minus {i} ({tag})')
                yield from asyncio.sleep(0.1)
            return "Blastoff!"
 
@@ -919,7 +919,7 @@ To create an iterable coroutine, subclass :py:class:`~typing.AsyncIterator`:
 
    async def countdown_4(tag: str, n: int) -> str:
        async for i in arange(n, 0, -1):
-           print('T-minus {} ({})'.format(i, tag))
+           print(f'T-minus {i} ({tag})')
            await asyncio.sleep(0.1)
        return "Blastoff!"
 
@@ -941,7 +941,7 @@ generator type as the return type:
    @asyncio.coroutine
    def countdown_2(tag: str, count: int) -> Generator[Any, None, str]:
        while count > 0:
-           print('T-minus {} ({})'.format(count, tag))
+           print(f'T-minus {count} ({tag})')
            yield from asyncio.sleep(0.1)
            count -= 1
        return "Blastoff!"
@@ -1045,7 +1045,7 @@ a subtype of (that is, compatible with) ``Mapping[str, object]``, since
 
    def print_typed_dict(obj: Mapping[str, object]) -> None:
        for key, value in obj.items():
-           print('{}: {}'.format(key, value))
+           print(f'{key}: {value}')
 
    print_typed_dict(Movie(name='Toy Story', year=1995))  # OK
 

docs/source/mypy_daemon.rst

@@ -177,7 +177,7 @@ In this example, the function ``format_id()`` has no annotation:
 .. code-block:: python
 
    def format_id(user):
-       return "User: {}".format(user)
+       return f"User: {user}"
 
    root = format_id(0)