Make some internal __init__ arguments positional/keyword-only

This is to make the code more readable/consistent.

Note that `Select` is actually public, but the constructor is not meant
to be used by users.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

src/frequenz/channels/_anycast.py

@@ -309,7 +309,7 @@ class _Sender(Sender[_T]):
     method.
     """
 
-    def __init__(self, channel: Anycast[_T]) -> None:
+    def __init__(self, channel: Anycast[_T], /) -> None:
         """Initialize this sender.
 
         Args:
@@ -377,7 +377,7 @@ class _Receiver(Receiver[_T]):
     method.
     """
 
-    def __init__(self, channel: Anycast[_T]) -> None:
+    def __init__(self, channel: Anycast[_T], /) -> None:
         """Initialize this receiver.
 
         Args:

src/frequenz/channels/_broadcast.py

@@ -279,7 +279,7 @@ def new_receiver(self, *, name: str | None = None, limit: int = 50) -> Receiver[
         Returns:
             A new receiver attached to this channel.
         """
-        recv: _Receiver[_T] = _Receiver(name, limit, self)
+        recv: _Receiver[_T] = _Receiver(self, name=name, limit=limit)
         self._receivers[hash(recv)] = weakref.ref(recv)
         if self.resend_latest and self._latest is not None:
             recv.enqueue(self._latest)
@@ -308,7 +308,7 @@ class _Sender(Sender[_T]):
     method.
     """
 
-    def __init__(self, channel: Broadcast[_T]) -> None:
+    def __init__(self, channel: Broadcast[_T], /) -> None:
         """Initialize this sender.
 
         Args:
@@ -364,21 +364,23 @@ class _Receiver(Receiver[_T]):
     method.
     """
 
-    def __init__(self, name: str | None, limit: int, channel: Broadcast[_T]) -> None:
+    def __init__(
+        self, channel: Broadcast[_T], /, *, name: str | None, limit: int
+    ) -> None:
         """Initialize this receiver.
 
         Broadcast receivers have their own buffer, and when messages are not
         being consumed fast enough and the buffer fills up, old messages will
         get dropped just in this receiver.
 
         Args:
+            channel: a reference to the Broadcast channel that this receiver
+                belongs to.
             name: A name to identify the receiver in the logs. If `None` an
                 `id(self)`-based name will be used.  This is only for debugging
                 purposes, it will be shown in the string representation of the
                 receiver.
             limit: Number of messages the receiver can hold in its buffer.
-            channel: a reference to the Broadcast channel that this receiver
-                belongs to.
         """
         self._name: str = name if name is not None else f"{id(self):_}"
         """The name to identify the receiver.
@@ -392,7 +394,7 @@ def __init__(self, name: str | None, limit: int, channel: Broadcast[_T]) -> None
         self._q: deque[_T] = deque(maxlen=limit)
         """The receiver's internal message queue."""
 
-    def enqueue(self, message: _T) -> None:
+    def enqueue(self, message: _T, /) -> None:
         """Put a message into this receiver's queue.
 
         To be called by broadcast senders.  If the receiver's queue is already

src/frequenz/channels/_receiver.py

@@ -240,7 +240,7 @@ def map(self, mapping_function: Callable[[_T_co], _U_co]) -> Receiver[_U_co]:
         Returns:
             A new receiver that applies the function on the received messages.
         """
-        return _Mapper(self, mapping_function)
+        return _Mapper(receiver=self, mapping_function=mapping_function)
 
 
 class ReceiverError(Error, Generic[_T_co]):
@@ -285,7 +285,7 @@ class _Mapper(Receiver[_U_co], Generic[_T_co, _U_co]):
     """
 
     def __init__(
-        self, receiver: Receiver[_T_co], mapping_function: Callable[[_T_co], _U_co]
+        self, *, receiver: Receiver[_T_co], mapping_function: Callable[[_T_co], _U_co]
     ) -> None:
         """Initialize this receiver mapper.
 

src/frequenz/channels/_select.py

@@ -170,7 +170,7 @@ class Selected(Generic[_T]):
     Please see [`select()`][frequenz.channels.select] for an example.
     """
 
-    def __init__(self, receiver: Receiver[_T]) -> None:
+    def __init__(self, receiver: Receiver[_T], /) -> None:
         """Initialize this selected result.
 
         The receiver is consumed immediately when creating the instance and the received