add with-statement

* with imported from mosquito (adaption of the code in 86a3e8dfb257e3af0ec141ee5d97717501d6e945 by @mosquito)
* encoding of file to utf-8
* added rudimentary test for with
* implement close function for all printers

escpos/constants.py

@@ -1,3 +1,4 @@
+#  -*- coding: utf-8 -*-
 """ Set of ESC/POS Commands (Constants)
 
 This module contains constants that are described in the esc/pos-documentation.

escpos/escpos.py

@@ -1,4 +1,5 @@
 #!/usr/bin/python
+#  -*- coding: utf-8 -*-
 """ Main class
 
 This module contains the abstract base class :py:class:`Escpos`.
@@ -38,6 +39,10 @@ class Escpos(object):
         :param columns: Text columns used by the printer. Defaults to 32."""
         self.columns = columns
 
+    def __del__(self):
+        """ call self.close upon deletion """
+        self.close()
+
     @abstractmethod
     def _raw(self, msg):
         """ Sends raw data to the printer
@@ -620,3 +625,89 @@ class Escpos(object):
             self._raw(PANEL_BUTTON_ON)
         else:
             self._raw(PANEL_BUTTON_OFF)
+
+
+class EscposIO(object):
+    """ESC/POS Printer IO object
+
+    Allows the class to be used together with the `with`-statement. You have to define a printer instance
+    and assign it to the EsposIO-class.
+    This example explains the usage:
+
+    .. code-block:: Python
+
+        with EscposIO(printer.Serial('/dev/ttyUSB0')) as p:
+            p.set(font='a', height=2, align='center', text_type='bold')
+            p.printer.set(align='left')
+            p.printer.image('logo.gif')
+            p.writelines('Big line\\n', font='b')
+            p.writelines('Привет')
+            p.writelines('BIG TEXT', width=2)
+
+    After the `with`-statement the printer automatically cuts the paper if `autocut` is `True`.
+    """
+
+    def __init__(self, printer, autocut=True, autoclose=True, **kwargs):
+        """
+        :param printer: An EscPos-printer object
+        :type printer: escpos.Escpos
+        :param autocut: If True, paper is automatically cut after the `with`-statement *default*: True
+        :param kwargs: These arguments will be passed to :py:meth:`escpos.Escpos.set()`
+        """
+        self.printer = printer
+        self.params = kwargs
+        self.autocut = autocut
+        self.autoclose = autoclose
+
+    def set(self, **kwargs):
+        """ Set the printer-parameters
+
+        Controls which parameters will be passed to :py:meth:`Escpos.set() <escpos.escpos.Escpos.set()>`.
+        For more information on the parameters see the :py:meth:`set() <escpos.escpos.Escpos.set()>`-methods
+        documentation. These parameters can also be passed with this class' constructor or the
+        :py:meth:`~escpos.escpos.EscposIO.writelines()`-method.
+
+        :param kwargs: keyword-parameters that will be passed to :py:meth:`Escpos.set() <escpos.escpos.Escpos.set()>`
+        """
+        self.params.update(kwargs)
+
+    def writelines(self, text, **kwargs):
+        params = dict(self.params)
+        params.update(kwargs)
+
+        if isinstance(text, six.text_type):
+            lines = text.split('\n')
+        elif isinstance(text, list) or isinstance(text, tuple):
+            lines = text
+        else:
+            lines = ["{0}".format(text), ]
+
+        # TODO check unicode handling
+        # TODO flush? or on print? (this should prob rather be handled by the _raw-method)
+        for line in lines:
+            self.printer.set(**params)
+            if isinstance(text, six.text_type):
+                self.printer.text(u"{0}\n".format(line))
+            else:
+                self.printer.text("{0}\n".format(line))
+
+    def close(self):
+        """ called upon closing the `with`-statement
+        """
+        self.printer.close()
+
+    def __enter__(self, **kwargs):
+        return self
+
+    def __exit__(self, type, value, traceback):
+        """
+
+        If :py:attr:`autocut <escpos.escpos.EscposIO.autocut>` is `True` (set by this class' constructor),
+        then :py:meth:`printer.cut() <escpos.escpos.Escpos.cut()>` will be called here.
+        """
+        if not (type is not None and issubclass(type, Exception)):
+            if self.autocut:
+                self.printer.cut()
+
+        if self.autoclose:
+            self.close()

escpos/exceptions.py

@@ -1,3 +1,4 @@
+#  -*- coding: utf-8 -*-
 """ ESC/POS Exceptions classes
 
 Result/Exit codes:

escpos/printer.py

@@ -1,5 +1,6 @@
 #!/usr/bin/python
-""" This module contains the implentations of abstract base class :py:class:`Escpos`.
+#  -*- coding: utf-8 -*-
+""" This module contains the implementations of abstract base class :py:class:`Escpos`.
 
 :author: `Manuel F Martinez <manpaz@bashlinux.com>`_ and others
 :organization: Bashlinux and `python-escpos <https://github.com/python-escpos>`_
@@ -82,7 +83,7 @@ class Usb(Escpos):
         """
         self.device.write(self.out_ep, msg, self.interface)
 
-    def __del__(self):
+    def close(self):
         """ Release USB interface """
         if self.device:
             usb.util.dispose_resources(self.device)
@@ -147,7 +148,7 @@ class Serial(Escpos):
         """
         self.device.write(msg)
 
-    def __del__(self):
+    def close(self):
         """ Close Serial interface """
         if self.device is not None:
             self.device.flush()
@@ -207,7 +208,7 @@ class Network(Escpos):
         """
         self.device.sendall(msg)
 
-    def __del__(self):
+    def close(self):
         """ Close TCP connection """
         self.device.shutdown(socket.SHUT_RDWR)
         self.device.close()
@@ -255,7 +256,7 @@ class File(Escpos):
         """
         self.device.write(msg)
 
-    def __del__(self):
+    def close(self):
         """ Close system file """
         self.device.flush()
         self.device.close()
@@ -294,3 +295,6 @@ class Dummy(Escpos):
     def output(self):
         """ Get the data that was sent to this printer """
         return b''.join(self._output_list)
+
+    def close(self):
+        pass

test/test_with_statement.py

@@ -0,0 +1,24 @@
+#!/usr/bin/python
+"""test the facility which enables usage of the with-statement
+
+:author: `Patrick Kanzler <patrick.kanzler@fablab.fau.de>`_
+:organization: `python-escpos <https://github.com/python-escpos>`_
+:copyright: Copyright (c) 2016 `python-escpos <https://github.com/python-escpos>`_
+:license: GNU GPL v3
+"""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import escpos.printer as printer
+import escpos.escpos as escpos
+import os
+
+def test_with_statement():
+    """Use with statement"""
+    dummy_printer = printer.Dummy()
+    with escpos.EscposIO(dummy_printer) as p:
+            p.writelines('Some text.\n')
+    # TODO extend these tests as they don't really do anything at the moment