Separate open() and store connection in 'device'

src/escpos/printer/cups.py

@@ -20,6 +20,9 @@ try:
     import cups
 
     _DEP_PYCUPS = True
+    # Store server defaults before further configuration
+    DEFAULT_HOST = cups.getServer()
+    DEFAULT_PORT = cups.getPort()
 except ImportError:
     pass
 
@@ -89,36 +92,36 @@ class CupsPrinter(Escpos):
         :type port: int
         """
         Escpos.__init__(self, *args, **kwargs)
-        host, port = args or (
+        self.host, self.port = args or (
-            kwargs.get("host", cups.getServer()),
+            kwargs.get("host", DEFAULT_HOST),
-            kwargs.get("port", cups.getPort()),
+            kwargs.get("port", DEFAULT_PORT),
         )
-        cups.setServer(host)
+        self.tmpfile = tempfile.NamedTemporaryFile(delete=True)
-        cups.setPort(port)
-        self.conn = cups.Connection()
-        self.tmpfile = None
         self.printer_name = printer_name
         self.job_name = ""
         self.pending_job = False
-        self.open()
 
     @property
     def printers(self):
         """Available CUPS printers."""
-        return self.conn.getPrinters()
+        return self.device.getPrinters()
 
     def open(self, job_name="python-escpos"):
         """Set up a new print job and target the printer.
 
         A call to this method is required to send new jobs to
-        the same CUPS connection.
+        the same CUPS connection after close.
 
         Defaults to default CUPS printer.
         Creates a new temporary file buffer.
         """
+        cups.setServer(self.host)
+        cups.setPort(self.port)
+        self.device = cups.Connection()
         self.job_name = job_name
         if self.printer_name not in self.printers:
-            self.printer_name = self.conn.getDefault()
+            self.printer_name = self.device.getDefault()
+        if self.tmpfile.closed:
             self.tmpfile = tempfile.NamedTemporaryFile(delete=True)
 
     def _raw(self, msg):
@@ -141,7 +144,7 @@ class CupsPrinter(Escpos):
             # Rewind tempfile
             self.tmpfile.seek(0)
             # Print temporary file via CUPS printer.
-            self.conn.printFile(
+            self.device.printFile(
                 self.printer_name,
                 self.tmpfile.name,
                 self.job_name,
@@ -173,8 +176,9 @@ class CupsPrinter(Escpos):
 
         Send pending job to the printer if needed.
         """
+        if not self._device:
+            return
         if self.pending_job:
             self.send()
-        if self.conn:
         print("Closing CUPS connection to printer {}".format(self.printer_name))
-            self.conn = None
+        self.device = None

src/escpos/printer/file.py

@@ -48,13 +48,12 @@ class File(Escpos):
         Escpos.__init__(self, *args, **kwargs)
         self.devfile = devfile
         self.auto_flush = auto_flush
-        self.open()
 
     def open(self):
         """Open system file."""
         self.device = open(self.devfile, "wb")
 
-        if self.device is None:
+        if not self.device:
             print("Could not open the specified file {0}".format(self.devfile))
 
     def flush(self):
@@ -73,6 +72,8 @@ class File(Escpos):
 
     def close(self):
         """Close system file."""
-        if self.device is not None:
+        if not self._device:
+            return
         self.device.flush()
         self.device.close()
+        self.device = None

src/escpos/printer/lp.py

@@ -72,12 +72,11 @@ class LP(Escpos):
         Escpos.__init__(self, *args, **kwargs)
         self.printer_name = printer_name
         self.auto_flush = kwargs.get("auto_flush", True)
-        self.open()
 
     @dependency_linux_lp
     def open(self):
         """Invoke _lp_ in a new subprocess and wait for commands."""
-        self.lp = subprocess.Popen(
+        self.device = subprocess.Popen(
             ["lp", "-d", self.printer_name, "-o", "raw"],
             stdin=subprocess.PIPE,
             stdout=open(os.devnull, "w"),
@@ -85,15 +84,18 @@ class LP(Escpos):
 
     def close(self):
         """Stop the subprocess."""
-        self.lp.terminate()
+        if not self._device:
+            return
+        self.device.terminate()
+        self.device = None
 
     def flush(self):
         """End line and wait for new commands."""
-        if self.lp.stdin.writable():
+        if self.device.stdin.writable():
-            self.lp.stdin.write(b"\n")
+            self.device.stdin.write(b"\n")
-        if self.lp.stdin.closed is False:
+        if self.device.stdin.closed is False:
-            self.lp.stdin.close()
+            self.device.stdin.close()
-        self.lp.wait()
+        self.device.wait()
         self.open()
 
     def _raw(self, msg):
@@ -102,8 +104,8 @@ class LP(Escpos):
         :param msg: arbitrary code to be printed
         :type msg: bytes
         """
-        if self.lp.stdin.writable():
+        if self.device.stdin.writable():
-            self.lp.stdin.write(msg)
+            self.device.stdin.write(msg)
         else:
             raise Exception("Not a valid pipe for lp process")
         if self.auto_flush:

src/escpos/printer/network.py

@@ -61,7 +61,6 @@ class Network(Escpos):
         self.host = host
         self.port = port
         self.timeout = timeout
-        self.open()
 
     def open(self):
         """Open TCP socket with ``socket``-library and set it as escpos device."""
@@ -69,7 +68,7 @@ class Network(Escpos):
         self.device.settimeout(self.timeout)
         self.device.connect((self.host, self.port))
 
-        if self.device is None:
+        if not self.device:
             print("Could not open socket for {0}".format(self.host))
 
     def _raw(self, msg):
@@ -86,9 +85,11 @@ class Network(Escpos):
 
     def close(self):
         """Close TCP connection."""
-        if self.device is not None:
+        if not self._device:
+            return
         try:
             self.device.shutdown(socket.SHUT_RDWR)
         except socket.error:
             pass
         self.device.close()
+        self.device = None

src/escpos/printer/serial.py

@@ -111,12 +111,10 @@ class Serial(Escpos):
         self.xonxoff = xonxoff
         self.dsrdtr = dsrdtr
 
-        self.open()
-
     @dependency_pyserial
     def open(self):
         """Set up serial port and set is as escpos device."""
-        if self.device is not None and self.device.is_open:
+        if self.device and self.device.is_open:
             self.close()
         self.device = serial.Serial(
             port=self.devfile,
@@ -129,7 +127,7 @@ class Serial(Escpos):
             dsrdtr=self.dsrdtr,
         )
 
-        if self.device is not None:
+        if self.device:
             print("Serial printer enabled")
         else:
             print("Unable to open serial printer on: {0}".format(str(self.devfile)))
@@ -148,6 +146,9 @@ class Serial(Escpos):
 
     def close(self):
         """Close Serial interface."""
-        if self.device is not None and self.device.is_open:
+        if not self._device:
+            return
+        if self.device.is_open:
             self.device.flush()
             self.device.close()
+        self.device = None

src/escpos/printer/usb.py

@@ -95,20 +95,16 @@ class Usb(Escpos):
         self.in_ep = in_ep
         self.out_ep = out_ep
 
-        usb_args = usb_args or {}
+        self.usb_args = usb_args or {}
         if idVendor:
-            usb_args["idVendor"] = idVendor
+            self.usb_args["idVendor"] = idVendor
         if idProduct:
-            usb_args["idProduct"] = idProduct
+            self.usb_args["idProduct"] = idProduct
-        self.open(usb_args)
 
     @dependency_usb
-    def open(self, usb_args):
+    def open(self):
-        """Search device on USB tree and set it as escpos device.
+        """Search device on USB tree and set it as escpos device."""
-
+        self.device = usb.core.find(**self.usb_args)
-        :param usb_args: USB arguments
-        """
-        self.device = usb.core.find(**usb_args)
         if self.device is None:
             raise USBNotFoundError("Device not found or cable not plugged in.")
 
@@ -157,6 +153,7 @@ class Usb(Escpos):
     @dependency_usb
     def close(self):
         """Release USB interface."""
-        if self.device:
+        if not self._device:
+            return
         usb.util.dispose_resources(self.device)
         self.device = None

src/escpos/printer/win32raw.py

@@ -77,29 +77,27 @@ class Win32Raw(Escpos):
             self.printer_name = printer_name
         else:
             self.printer_name = win32print.GetDefaultPrinter()
-        self.hPrinter = None
-        self.open()
 
     @dependency_win32print
     def open(self, job_name="python-escpos"):
         """Open connection to default printer."""
         if self.printer_name is None:
             raise Exception("Printer not found")
-        self.hPrinter = win32print.OpenPrinter(self.printer_name)
+        self.device = win32print.OpenPrinter(self.printer_name)
         self.current_job = win32print.StartDocPrinter(
-            self.hPrinter, 1, (job_name, None, "RAW")
+            self.device, 1, (job_name, None, "RAW")
         )
-        win32print.StartPagePrinter(self.hPrinter)
+        win32print.StartPagePrinter(self.device)
 
     @dependency_win32print
     def close(self):
         """Close connection to default printer."""
-        if not self.hPrinter:
+        if not self._device:
             return
-        win32print.EndPagePrinter(self.hPrinter)
+        win32print.EndPagePrinter(self.device)
-        win32print.EndDocPrinter(self.hPrinter)
+        win32print.EndDocPrinter(self.device)
-        win32print.ClosePrinter(self.hPrinter)
+        win32print.ClosePrinter(self.device)
-        self.hPrinter = None
+        self.device = None
 
     @dependency_win32print
     def _raw(self, msg):
@@ -110,6 +108,6 @@ class Win32Raw(Escpos):
         """
         if self.printer_name is None:
             raise Exception("Printer not found")
-        if self.hPrinter is None:
+        if not self.device:
             raise Exception("Printer job not opened")
-        win32print.WritePrinter(self.hPrinter, msg)
+        win32print.WritePrinter(self.device, msg)