Removed old code, added new files in src/ using classes for each moving part.

src/printer.py

@@ -0,0 +1,95 @@
+# Importing the module to mage the connection to the printer.
+from escpos.printer import Usb, USBNotFoundError
+from time import sleep, gmtime, strftime
+import os.path
+
+
+class Printer(object):
+    """
+    # The connection is based on the ESC/POS library
+
+    ## Connection to the USB printer
+
+    ## Making sure the printer is alive
+
+    ## Making sure it has paper
+
+    ## Define default print settings
+
+    ## Print starting message, log time of first print, cut.
+
+    ## Annonce readyness : return a positive pong message.
+    """
+
+    # Is the printer ready to accept a new print ?
+    ready = False
+
+    def __init__(self, app):
+        super(Printer, self).__init__()
+        self.app = app
+        self.ready = False
+        self.printer = None
+
+    def init_printer(self, device_id,vendor_id):
+        try:
+            p = Usb(vendor_id, device_id)
+        except USBNotFoundError as e:
+            self.app.logger.error("The USB device is not plugged in, aborting...")
+            exit(-1)
+        waiting_elapsed = 10
+
+        # Is the printer online ? Is the communication with the printer successfull ?
+        while not p.is_online():
+            self.app.logger.debug('Waiting for printer to get online...')
+            sleep(1)
+            waiting_elapsed -= 1
+            if waiting_elapsed < 1:
+                self.app.logger.error('Printer took more than 10 seconds to get online, aborting...')
+                return False
+
+        # Let's check paper status.
+        ps = p.paper_status()
+        if ps == 0:
+            self.app.logger.error('Printer has no more paper, aborting...')
+            return False
+        elif ps == 1:
+            self.app.logger.warning('Printer needs paper to be changed very soon ! ')
+            sleep(5)
+        elif ps == 0:
+            self.app.logger.debug('Printer has paper, good to go')
+
+        # We're going to print a little text to let know that we're good, as a final check.
+        p.textln("Hello world ! \nStarting up at " + strftime("%Y-%m-%d %H:%M:%S", gmtime()))
+        p.set(align='center', font='a', bold=False, underline=0, width=1, height=1, density=9, invert=False, smooth=False, flip=False, double_width=False, double_height=False, custom_size=False)
+        p.textln("------------------")
+        p.qr("Hello World ! :)")
+        p.image("../configuration/hello_world.png",center=True)
+        p.cut()
+
+        self.printer = p;
+        self.ready = True;
+        return True
+
+    def print_sms(self, msg):
+        clean_msg = str(msg)
+
+        if len(clean_msg) > 256 or len(clean_msg) < 10 :
+            self.app.logger.warning("Could not print message of this length :" + len(clean_msg))
+            return False
+        else :
+            self.printer.textln(strftime("%Y-%m-%d %H:%M:%S", gmtime()))
+            self.printer.textln(clean_msg)
+
+    def print_img(self, path):
+
+        if os.path.isfile(str(path)):
+            pass
+        else:
+            self.app.logger.warning("File does not exist : " + str(path))
+
+        try:
+            self.printer.image(path)
+        except Exception as e:
+            return e
+        else:
+            self.app.logging.debug("Printed an image : " + str(path))