Move _device type annotations to __init__()

src/escpos/printer/cups.py

@@ -74,8 +74,6 @@ class CupsPrinter(Escpos):
 
     """
 
-    _device: Union[Literal[False], Literal[None], cups.Connection] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -105,6 +103,10 @@ class CupsPrinter(Escpos):
         self.job_name = ""
         self.pending_job = False
 
+        self._device: Union[
+            Literal[False], Literal[None], Type[cups.Connection]
+        ] = False
+
     @property
     def printers(self) -> dict:
         """Available CUPS printers."""

src/escpos/printer/file.py

@@ -34,8 +34,6 @@ class File(Escpos):
 
     """
 
-    _device: Union[Literal[False], Literal[None], IO[bytes]] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -55,6 +53,8 @@ class File(Escpos):
         self.devfile = devfile
         self.auto_flush = auto_flush
 
+        self._device: Union[Literal[False], Literal[None], IO[bytes]] = False
+
     def open(self, raise_not_found: bool = True) -> None:
         """Open system file.
 

src/escpos/printer/lp.py

@@ -54,8 +54,6 @@ class LP(Escpos):
 
     """
 
-    _device: Union[Literal[False], Literal[None], subprocess.Popen] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -77,6 +75,8 @@ class LP(Escpos):
         self.auto_flush = kwargs.get("auto_flush", False)
         self._flushed = False
 
+        self._device: Union[Literal[False], Literal[None], subprocess.Popen] = False
+
     @property
     def printers(self) -> dict:
         """Available CUPS printers."""

src/escpos/printer/network.py

@@ -48,8 +48,6 @@ class Network(Escpos):
 
     """
 
-    _device: Union[Literal[False], Literal[None], socket.socket] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -78,6 +76,8 @@ class Network(Escpos):
         self.port = port
         self.timeout = timeout
 
+        self._device: Union[Literal[False], Literal[None], socket.socket] = False
+
     def open(self, raise_not_found: bool = True) -> None:
         """Open TCP socket with ``socket``-library and set it as escpos device.
 

src/escpos/printer/serial.py

@@ -64,8 +64,6 @@ class Serial(Escpos):
 
     """
 
-    _device: Union[Literal[False], Literal[None], serial.Serial] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -116,6 +114,8 @@ class Serial(Escpos):
         self.xonxoff = xonxoff
         self.dsrdtr = dsrdtr
 
+        self._device: Union[Literal[False], Literal[None], serial.Serial] = False
+
     @dependency_pyserial
     def open(self, raise_not_found: bool = True) -> None:
         """Set up serial port and set is as escpos device.

src/escpos/printer/usb.py

@@ -63,8 +63,6 @@ class Usb(Escpos):
 
     """
 
-    _device: Union[Literal[False], Literal[None], Type[usb.core.Device]] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -105,6 +103,10 @@ class Usb(Escpos):
         if idProduct:
             self.usb_args["idProduct"] = idProduct
 
+        self._device: Union[
+            Literal[False], Literal[None], Type[usb.core.Device]
+        ] = False
+
     @dependency_usb
     def open(self, raise_not_found: bool = True) -> None:
         """Search device on USB tree and set it as escpos device.

src/escpos/printer/win32raw.py

@@ -65,10 +65,6 @@ class Win32Raw(Escpos):
 
     """
 
-    _device: Union[
-        Literal[False], Literal[None], "_win32typing.PyPrinterHANDLE"  # noqa: F821
-    ] = False
-
     @staticmethod
     def is_usable() -> bool:
         """Indicate whether this printer class is usable.
@@ -85,6 +81,10 @@ class Win32Raw(Escpos):
         self.printer_name = printer_name
         self.job_name = ""
 
+        self._device: Union[
+            Literal[False], Literal[None], "_win32typing.PyPrinterHANDLE"  # noqa: F821
+        ] = False
+
     @property
     @dependency_win32print
     def printers(self) -> dict: