Remove semicolons, syntax enhancements, remove unused constant.

src/escpos/constants.py

@@ -252,5 +252,4 @@ S_RASTER_Q  = _PRINT_RASTER_IMG(b'\x03')  # Set raster image quadruple
 
 # Status Command
 RT_STATUS_ONLINE = DLE + EOT +  b'\x01';
-RT_STATUS_OFFLINECAUSE = DLE + EOT +  b'\x02';
 RT_MASK_ONLINE = 8;

src/escpos/escpos.py

@@ -35,7 +35,7 @@ from .constants import CD_KICK_DEC_SEQUENCE, CD_KICK_5, CD_KICK_2, PAPER_FULL_CU
 from .constants import HW_RESET, HW_SELECT, HW_INIT
 from .constants import CTL_VT, CTL_HT, CTL_CR, CTL_FF, CTL_LF, CTL_SET_HT, PANEL_BUTTON_OFF, PANEL_BUTTON_ON
 from .constants import TXT_STYLE
-from .constants import RT_STATUS_ONLINE, RT_STATUS_OFFLINECAUSE, RT_MASK_ONLINE
+from .constants import RT_STATUS_ONLINE, RT_MASK_ONLINE
 
 from .exceptions import BarcodeTypeError, BarcodeSizeError, TabPosError
 from .exceptions import CashDrawerError, SetVariableError, BarcodeCodeError
@@ -80,7 +80,10 @@ class Escpos(object):
         pass
 
     def _read(self, msg):
-        raise NotImplementedError(); 
+        """ Returns a NotImplementedError if the instance of the class doesn't override this method.
+        :raises NotImplementedError
+        """
+        raise NotImplementedError()
 
     def image(self, img_source, high_density_vertical=True, high_density_horizontal=True, impl="bitImageRaster",
               fragment_height=960):
@@ -738,18 +741,20 @@ class Escpos(object):
         else:
             self._raw(PANEL_BUTTON_OFF)
 
-    def queryStatus(self):
+    def query_status(self):
+        """ Queries the printer for its status, and returns an array of integers containing it.
+        :rtype: array(integer)"""
         self._raw(RT_STATUS_ONLINE)
         time.sleep(1)
-        status = self._read();
-        if (len(status) > 0):
-            return status;
-        else:
-            return [8];
+        status = self._read()
+        return status or [8]
+
+    def is_online(self):
+        """ Queries the printer its online status.
+        When online, returns True; False otherwise.
+        :rtype: bool: True if online, False if offline."""
+        return (self.query_status()[0] & RT_MASK_ONLINE) == 0
 
-    def isOnline(self):
-        status = self.queryStatus()[0];
-        return ((status & RT_MASK_ONLINE) == 0);
 
 class EscposIO(object):
     """ESC/POS Printer IO object