foo.py

class Printer():
    """
    Print thing with my ESCPOS printer
    """
    def text(self, text):
        with open('/dev/usb/lp0', 'wb') as lp0:
            lp0.write(text.encode('cp437'))
            lp0.write(b'\n')
    def command(self, command):
        with open('/dev/usb/lp0', 'wb') as lp0:
            lp0.write(command)
            lp0.write(b'\n')
    def style(command_before, command_after):
        """
        Send a command before and a command after
        """
        def decorator(func):
            def wrapper(self, text):
                print(self)
                print(text)
                self.command(command_before)
                func(text)
                self.command(command_after)
            return wrapper
        return decorator
    @style((b'\x1D\x42\x31'), (b'\x1D\x42\x32')) #print white on black
    @style((b'\x1D\x21\x34'), (b'\x1D\y21\x00')) #print bigger
    def title(self, title_text):
        self.text(title_text)


class _BeforeAfterContext(object):
    def __init__(self, printer, before, after):
        self._printer = printer
        self._before = before
        self._after = after

    def __enter__(self):
        self._printer.write_line(self._before)

    def __exit__(self, exc_type, exc_val, exc_tb):
        if exc_val is None:
            # Don't send if an exception occurred
            return False
        self._printer.write_line(self._after)


class Printer():
    def __init__(self, device):
        self._device = device

    def write_line(self, data):
        self._device.write(data + b'\n')

    def style(self, before, after):
        return _BeforeAfterContext(self, before, after)


with open('/dev/usb/lp0', 'rb') as lp0:
    printer = Printer(lp0)
    with printer.style(b'\x1D\x42\x31', b'\x1D\x42\x32'): #print white on black
        with printer.style(b'\x1D\x21\x34', b'\x1D\y21\x00'): #print bigger
            printer.write_line(title_text)