start removal of six and improve type annotation (#607)

* fix unfinished Python2 -> 3 translation
* remove some six usage
* annotate
* fix regression in Six removal
* mypy: self.enf is always defined
* fix return type of cups.py
* Usb idVendor/idProduct are integers
* self.default_args is always defined
* tweak usb_args, PEP589 is better
* lp.py: reassure mypy
* correctly cast call to CashDrawerError()
* update CUPS test
* add missing close() method in metaclass
* document a bug in typeshed
* query_status() returns bytes as seen in constants.py
* remove more SIX usage
* test examples too
* remove type comment where type is annotated
* adapt behavior of cups printer to match other implementations

---------

Co-authored-by: Patrick Kanzler <dev@pkanzler.de>
Co-authored-by: Patrick Kanzler <4189642+patkan@users.noreply.github.com>

examples/codepage_tables.py

@@ -3,8 +3,6 @@
 
 import sys
 
-import six
-
 from escpos import printer
 from escpos.constants import (
     CODEPAGE_CHANGE,
@@ -38,7 +36,7 @@ def print_codepage(printer, codepage):
     """Print a codepage."""
     if codepage.isdigit():
         codepage = int(codepage)
-        printer._raw(CODEPAGE_CHANGE + six.int2byte(codepage))
+        printer._raw(CODEPAGE_CHANGE + bytes((codepage,)))
         printer._raw("after")
     else:
         printer.charcode(codepage)
@@ -58,7 +56,9 @@ def print_codepage(printer, codepage):
         printer.set()
 
         for y in range(0, 16):
-            byte = six.int2byte(x * 16 + y)
+            byte = bytes(
+                (x * 16 + y),
+            )
 
             if byte in (ESC, CTL_LF, CTL_FF, CTL_CR, CTL_HT, CTL_VT):
                 byte = " "

examples/weather.py

@@ -18,8 +18,8 @@ import calendar
 import json
 import os
 import time
-import urllib
 from datetime import datetime
+from urllib.request import urlopen
 
 from escpos.printer import Usb
 
@@ -93,7 +93,7 @@ url = (
     + LONG
     + "?exclude=[alerts,minutely,hourly,flags]&units=si"
 )  # change last bit to 'us' for Fahrenheit
-response = urllib.urlopen(url)
+response = urlopen(url)
 data = json.loads(response.read())
 
 printer.print_and_feed(n=1)

src/escpos/__init__.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 """python-escpos enables you to manipulate escpos-printers."""
 
-__all__ = ["constants", "escpos", "exceptions", "printer"]
+__all__ = ["constants", "escpos", "exceptions", "printer", "__version__"]
 
 try:
     from .version import version as __version__  # noqa

src/escpos/capabilities.py

@@ -11,7 +11,6 @@ from tempfile import mkdtemp
 from typing import Any, Dict, Optional, Type
 
 import importlib_resources
-import six
 import yaml
 
 logging.basicConfig()
@@ -92,7 +91,7 @@ class NotSupported(Exception):
 BARCODE_B = "barcodeB"
 
 
-class BaseProfile(object):
+class BaseProfile:
     """This represents a printer profile.
 
     A printer profile knows about the number of columns, supported
@@ -111,20 +110,22 @@ class BaseProfile(object):
         Makes sure that the requested `font` is valid.
         """
         font = {"a": 0, "b": 1}.get(font, font)
-        if not six.text_type(font) in self.fonts:
+        if not str(font) in self.fonts:
             raise NotSupported(f'"{font}" is not a valid font in the current profile')
         return font
 
-    def get_columns(self, font):
+    def get_columns(self, font) -> int:
         """Return the number of columns for the given font."""
         font = self.get_font(font)
-        return self.fonts[six.text_type(font)]["columns"]
+        columns = self.fonts[str(font)]["columns"]
+        assert type(columns) is int
+        return columns
 
-    def supports(self, feature):
+    def supports(self, feature) -> bool:
         """Return true/false for the given feature."""
         return self.features.get(feature)
 
-    def get_code_pages(self):
+    def get_code_pages(self) -> Dict[str, int]:
         """Return the support code pages as a ``{name: index}`` dict."""
         return {v: k for k, v in self.codePages.items()}
 
@@ -161,7 +162,7 @@ def get_profile_class(name: str) -> Type[BaseProfile]:
     return CLASS_CACHE[name]
 
 
-def clean(s):
+def clean(s: str) -> str:
     """Clean profile name."""
     # Remove invalid characters
     s = re.sub("[^0-9a-zA-Z_]", "", s)
@@ -180,14 +181,14 @@ class Profile(ProfileBaseClass):
     For users, who want to provide their own profile.
     """
 
-    def __init__(self, columns=None, features=None):
+    def __init__(self, columns: Optional[int] = None, features=None) -> None:
         """Initialize profile."""
         super(Profile, self).__init__()
 
         self.columns = columns
         self.features = features or {}
 
-    def get_columns(self, font):
+    def get_columns(self, font) -> int:
         """Get column count of printer."""
         if self.columns is not None:
             return self.columns

src/escpos/cli.py

@@ -20,15 +20,13 @@ except ImportError:
     pass  # noqa
 import sys
 
-import six
-
 from . import config
 from . import printer as escpos_printer_module
 from . import version
 
 
 # Must be defined before it's used in DEMO_FUNCTIONS
-def str_to_bool(string):
+def str_to_bool(string: str) -> bool:
     """Convert string to bool.
 
     Used as a type in argparse so that we get back a proper
@@ -563,7 +561,7 @@ def generate_parser() -> argparse.ArgumentParser:
     return parser
 
 
-def main():
+def main() -> None:
     """Handle main entry point of CLI script.
 
     Handles loading of configuration and creating and processing of command
@@ -580,9 +578,7 @@ def main():
     if not args_dict:
         parser.print_help()
         sys.exit()
-    command_arguments = dict(
+    command_arguments = dict([k, v] for k, v in args_dict.items() if v is not None)
-        [k, v] for k, v in six.iteritems(args_dict) if v is not None
-    )
 
     # If version should be printed, do this, then exit
     print_version = command_arguments.pop("version", None)
@@ -621,7 +617,7 @@ def main():
         globals()[target_command](**command_arguments)
 
 
-def demo(printer, **kwargs):
+def demo(printer, **kwargs) -> None:
     """Print demos.
 
     Called when CLI is passed `demo`. This function

src/escpos/config.py

@@ -11,7 +11,7 @@ import yaml
 from . import exceptions, printer
 
 
-class Config(object):
+class Config:
     """Configuration handler class.
 
     This class loads configuration from a default or specified directory. It
@@ -21,7 +21,7 @@ class Config(object):
     _app_name = "python-escpos"
     _config_file = "config.yaml"
 
-    def __init__(self):
+    def __init__(self) -> None:
         """Initialize configuration.
 
         Remember to add anything that needs to be reset between configurations
@@ -33,7 +33,7 @@ class Config(object):
         self._printer_name = None
         self._printer_config = None
 
-    def _reset_config(self):
+    def _reset_config(self) -> None:
         """Clear the loaded configuration.
 
         If we are loading a changed config, we don't want to have leftover

src/escpos/constants.py

@@ -46,9 +46,7 @@ HW_RESET: bytes = ESC + b"\x3f\x0a\x00"  # Reset printer hardware
 # (TODO: Where is this specified?)
 
 # Cash Drawer (ESC p <pin> <on time: 2*ms> <off time: 2*ms>)
-_CASH_DRAWER = (
+_CASH_DRAWER = lambda m, t1="", t2="": ESC + b"p" + m + bytes((t1, t2))
-    lambda m, t1="", t2="": ESC + b"p" + m + six.int2byte(t1) + six.int2byte(t2)
-)
 
 #: decimal cash drawer kick sequence
 CD_KICK_DEC_SEQUENCE = (

src/escpos/escpos.py

@@ -9,13 +9,14 @@ This module contains the abstract base class :py:class:`Escpos`.
 :copyright: Copyright (c) 2012-2017 Bashlinux and python-escpos
 :license: MIT
 """
-
+from __future__ import annotations
 
 import textwrap
 import warnings
 from abc import ABCMeta, abstractmethod  # abstract base class support
 from re import match as re_match
-from typing import List, Literal, Optional, Union
+from types import TracebackType
+from typing import Any, Literal, Optional, Union
 
 import barcode
 import qrcode
@@ -107,8 +108,7 @@ SW_BARCODE_NAMES = {
 }
 
 
-@six.add_metaclass(ABCMeta)
+class Escpos(object, metaclass=ABCMeta):
-class Escpos(object):
     """ESC/POS Printer object.
 
     This class is the abstract base class for an Esc/Pos-printer. The printer implementations are children of this
@@ -154,6 +154,10 @@ class Escpos(object):
         """Open a printer device/connection."""
         pass
 
+    def close(self):
+        """Close a printer device/connection."""
+        pass
+
     @abstractmethod
     def _raw(self, msg: bytes) -> None:
         """Send raw data to the printer.
@@ -164,7 +168,7 @@ class Escpos(object):
         """
         pass
 
-    def _read(self):
+    def _read(self) -> bytes:
         """Read from printer.
 
         Returns a NotImplementedError if the instance of the class doesn't override this method.
@@ -250,7 +254,7 @@ class Escpos(object):
             header = (
                 GS
                 + b"v0"
-                + six.int2byte(density_byte)
+                + bytes((density_byte,))
                 + self._int_low_high(im.width_bytes, 2)
                 + self._int_low_high(im.height, 2)
             )
@@ -263,8 +267,8 @@ class Escpos(object):
             )
             tone = b"0"
             colors = b"1"
-            ym = six.int2byte(1 if high_density_vertical else 2)
+            ym = b"\x01" if high_density_vertical else b"\x02"
-            xm = six.int2byte(1 if high_density_horizontal else 2)
+            xm = b"\x01" if high_density_horizontal else b"\x02"
             header = tone + xm + ym + colors + img_header
             raster_data = im.to_raster_format()
             self._image_send_graphics_data(b"0", b"p", header + raster_data)
@@ -847,7 +851,7 @@ class Escpos(object):
         image = my_code.writer._image
         self.image(image, impl=impl, center=center)
 
-    def text(self, txt):
+    def text(self, txt: str) -> None:
         """Print alpha-numeric text.
 
         The text has to be encoded in the currently selected codepage.
@@ -856,10 +860,9 @@ class Escpos(object):
         :param txt: text to be printed
         :raises: :py:exc:`~escpos.exceptions.TextError`
         """
-        txt = six.text_type(txt)
+        self.magic.write(str(txt))
-        self.magic.write(txt)
 
-    def textln(self, txt=""):
+    def textln(self, txt: str = "") -> None:
         """Print alpha-numeric text with a newline.
 
         The text has to be encoded in the currently selected codepage.
@@ -870,7 +873,7 @@ class Escpos(object):
         """
         self.text(f"{txt}\n")
 
-    def ln(self, count=1):
+    def ln(self, count: int = 1) -> None:
         """Print a newline or more.
 
         :param count: number of newlines to print
@@ -881,7 +884,7 @@ class Escpos(object):
         if count > 0:
             self.text("\n" * count)
 
-    def block_text(self, txt, font="0", columns=None):
+    def block_text(self, txt, font="0", columns=None) -> None:
         """Print text wrapped to specific columns.
 
         Text has to be encoded in unicode.
@@ -1132,7 +1135,7 @@ class Escpos(object):
             try:
                 self._raw(CD_KICK_DEC_SEQUENCE(*pin))
             except TypeError as err:
-                raise CashDrawerError(err)
+                raise CashDrawerError(str(err))
 
     def linedisplay_select(self, select_display: bool = False) -> None:
         """Select the line display or the printer.
@@ -1265,10 +1268,10 @@ class Escpos(object):
         else:
             self._raw(PANEL_BUTTON_OFF)
 
-    def query_status(self, mode: bytes) -> List[int]:
+    def query_status(self, mode: bytes) -> bytes:
         """Query the printer for its status.
 
-        Returns an array of integers containing it.
+        Returns byte array containing it.
 
         :param mode: Integer that sets the status mode queried to the printer.
             - RT_STATUS_ONLINE: Printer status.
@@ -1288,7 +1291,7 @@ class Escpos(object):
             return False
         return not (status[0] & RT_MASK_ONLINE)
 
-    def paper_status(self):
+    def paper_status(self) -> int:  # could be IntEnum
         """Query the paper status of the printer.
 
         Returns 2 if there is plenty of paper, 1 if the paper has arrived to
@@ -1305,6 +1308,8 @@ class Escpos(object):
             return 1
         if status[0] & RT_MASK_PAPER == RT_MASK_PAPER:
             return 2
+        # not reached
+        return 0
 
     def target(self, type: str = "ROLL") -> None:
         """Select where to print to.
@@ -1359,7 +1364,7 @@ class Escpos(object):
         self._raw(BUZZER + six.int2byte(times) + six.int2byte(duration))
 
 
-class EscposIO(object):
+class EscposIO:
     r"""ESC/POS Printer IO object.
 
     Allows the class to be used together with the `with`-statement. You have to define a printer instance
@@ -1405,12 +1410,12 @@ class EscposIO(object):
         """
         self.params.update(kwargs)
 
-    def writelines(self, text, **kwargs):
+    def writelines(self, text: str, **kwargs) -> None:
         """Print text."""
         params = dict(self.params)
         params.update(kwargs)
 
-        if isinstance(text, six.text_type):
+        if isinstance(text, str):
             lines = text.split("\n")
         elif isinstance(text, list) or isinstance(text, tuple):
             lines = text
@@ -1423,23 +1428,22 @@ class EscposIO(object):
         # 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(f"{line}\n")
-            else:
             self.printer.text(f"{line}\n")
 
-    def close(self):
+    def close(self) -> None:
         """Close printer.
 
         Called upon closing the `with`-statement.
         """
         self.printer.close()
 
-    def __enter__(self, **kwargs):
+    def __enter__(self, **kwargs: Any) -> "EscposIO":
         """Enter context."""
         return self
 
-    def __exit__(self, type, value, traceback):
+    def __exit__(
+        self, type: type[BaseException], value: BaseException, traceback: TracebackType
+    ) -> None:
         """Cut and close if configured.
 
         If :py:attr:`autocut <escpos.escpos.EscposIO.autocut>` is `True` (set by this class' constructor),

src/escpos/exceptions.py

@@ -26,6 +26,8 @@ Result/Exit codes:
 :license: MIT
 """
 
+from typing import Optional
+
 
 class Error(Exception):
     """Base class for ESC/POS errors.
@@ -37,7 +39,7 @@ class Error(Exception):
 
     """
 
-    def __init__(self, msg, status=None):
+    def __init__(self, msg: str, status: Optional[int] = None) -> None:
         """Initialize Error object."""
         Exception.__init__(self)
         self.msg = msg
@@ -45,7 +47,7 @@ class Error(Exception):
         if status is not None:
             self.resultcode = status
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of Error."""
         return self.msg
 
@@ -64,13 +66,13 @@ class BarcodeTypeError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize BarcodeTypeError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 10
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of BarcodeTypeError."""
         return f"No Barcode type is defined ({self.msg})"
 
@@ -89,13 +91,13 @@ class BarcodeSizeError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize BarcodeSizeError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 20
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of BarcodeSizeError."""
         return f"Barcode size is out of range ({self.msg})"
 
@@ -114,13 +116,13 @@ class BarcodeCodeError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize BarcodeCodeError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 30
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of BarcodeCodeError."""
         return f"No Barcode code was supplied ({self.msg})"
 
@@ -137,13 +139,13 @@ class ImageSizeError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize ImageSizeError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 40
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of ImageSizeError."""
         return f"Image height is longer than 255px and can't be printed ({self.msg})"
 
@@ -160,13 +162,13 @@ class ImageWidthError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize ImageWidthError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 41
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of ImageWidthError."""
         return f"Image width is too large ({self.msg})"
 
@@ -184,13 +186,13 @@ class TextError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize TextError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 50
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of TextError."""
         return f"Text string must be supplied to the text() method ({self.msg})"
 
@@ -208,13 +210,13 @@ class CashDrawerError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize CashDrawerError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 60
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of CashDrawerError."""
         return f"Valid pin must be set to send pulse ({self.msg})"
 
@@ -235,13 +237,13 @@ class TabPosError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize TabPosError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 70
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of TabPosError."""
         return f"Valid tab positions must be in the range 0 to 16 ({self.msg})"
 
@@ -259,13 +261,13 @@ class CharCodeError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize CharCodeError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 80
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of CharCodeError."""
         return f"Valid char code must be set ({self.msg})"
 
@@ -283,13 +285,13 @@ class DeviceNotFoundError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize DeviceNotFoundError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 90
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of DeviceNotFoundError."""
         return f"Device not found ({self.msg})"
 
@@ -307,13 +309,13 @@ class USBNotFoundError(DeviceNotFoundError):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize USBNotFoundError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 91
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of USBNotFoundError."""
         return f"USB device not found ({self.msg})"
 
@@ -331,13 +333,13 @@ class SetVariableError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize SetVariableError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 100
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of SetVariableError."""
         return f"Set variable out of range ({self.msg})"
 
@@ -358,13 +360,13 @@ class ConfigNotFoundError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize ConfigNotFoundError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 200
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of ConfigNotFoundError."""
         return f"Configuration not found ({self.msg})"
 
@@ -382,13 +384,13 @@ class ConfigSyntaxError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize ConfigSyntaxError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 210
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of ConfigSyntaxError."""
         return f"Configuration syntax is invalid ({self.msg})"
 
@@ -406,12 +408,12 @@ class ConfigSectionMissingError(Error):
 
     """
 
-    def __init__(self, msg=""):
+    def __init__(self, msg: str = "") -> None:
         """Initialize ConfigSectionMissingError object."""
         Error.__init__(self, msg)
         self.msg = msg
         self.resultcode = 220
 
-    def __str__(self):
+    def __str__(self) -> str:
         """Return string representation of ConfigSectionMissingError."""
         return f"Configuration section is missing ({self.msg})"

src/escpos/image.py

@@ -10,12 +10,12 @@ This module contains the image format handler :py:class:`EscposImage`.
 
 
 import math
-from typing import Union
+from typing import Iterator, Union
 
 from PIL import Image, ImageOps
 
 
-class EscposImage(object):
+class EscposImage:
     """
     Load images in, and output ESC/POS formats.
 
@@ -23,7 +23,7 @@ class EscposImage(object):
     PIL, rather than spend CPU cycles looping over pixels.
     """
 
-    def __init__(self, img_source: Union[Image.Image, str]):
+    def __init__(self, img_source: Union[Image.Image, str]) -> None:
         """Load in an image.
 
         :param img_source: PIL.Image, or filename to load one from.
@@ -65,7 +65,7 @@ class EscposImage(object):
         _, height_pixels = self._im.size
         return height_pixels
 
-    def to_column_format(self, high_density_vertical: bool = True):
+    def to_column_format(self, high_density_vertical: bool = True) -> Iterator[bytes]:
         """Extract slices of an image as equal-sized blobs of column-format data.
 
         :param high_density_vertical: Printed line height in dots
@@ -82,7 +82,7 @@ class EscposImage(object):
             yield (im_bytes)
             left += line_height
 
-    def to_raster_format(self):
+    def to_raster_format(self) -> bytes:
         """Convert image to raster-format binary."""
         return self._im.tobytes()
 

src/escpos/katakana.py

@@ -11,7 +11,7 @@ except ImportError:
     jaconv = None
 
 
-def encode_katakana(text):
+def encode_katakana(text: str) -> bytes:
     """I don't think this quite works yet."""
     encoded = []
     for char in text:

src/escpos/magicencode.py

@@ -23,7 +23,7 @@ from .constants import CODEPAGE_CHANGE
 from .exceptions import Error
 
 
-class Encoder(object):
+class Encoder:
     """Take available code spaces and pick the right one for a given character.
 
     Note: To determine the code page, it needs to do the conversion, and
@@ -202,7 +202,7 @@ def split_writable_text(encoder, text, encoding):
     return text, None
 
 
-class MagicEncode(object):
+class MagicEncode:
     """Help switching to the right code page.
 
     A helper that helps us to automatically switch to the right
@@ -292,7 +292,7 @@ class MagicEncode(object):
 
     def write_with_encoding(self, encoding, text):
         """Write the text and inject necessary codepage switches."""
-        if text is not None and type(text) is not six.text_type:
+        if text is not None and type(text) is not str:
             raise Error(
                 f"The supplied text has to be unicode, but is of type {type(text)}."
             )

src/escpos/printer/cups.py

@@ -84,7 +84,7 @@ class CupsPrinter(Escpos):
         return is_usable()
 
     @dependency_pycups
-    def __init__(self, printer_name: str = "", *args, **kwargs):
+    def __init__(self, printer_name: str = "", *args, **kwargs) -> None:
         """Class constructor for CupsPrinter.
 
         :param printer_name: CUPS printer name (Optional)
@@ -163,11 +163,10 @@ class CupsPrinter(Escpos):
                 return
         logging.info("CupsPrinter printer enabled")
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Append any command sent in raw format to temporary file.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
         self.pending_job = True
         try:
@@ -176,8 +175,9 @@ class CupsPrinter(Escpos):
             self.pending_job = False
             raise TypeError("Bytes required. Printer job not opened")
 
-    def send(self):
+    def send(self) -> None:
         """Send the print job to the printer."""
+        assert self.device
         if self.pending_job:
             # Rewind tempfile
             self.tmpfile.seek(0)
@@ -190,7 +190,7 @@ class CupsPrinter(Escpos):
             )
         self._clear()
 
-    def _clear(self):
+    def _clear(self) -> None:
         """Finish the print job.
 
         Remove temporary file.
@@ -198,18 +198,18 @@ class CupsPrinter(Escpos):
         self.tmpfile.close()
         self.pending_job = False
 
-    def _read(self):
+    def _read(self) -> bytes:
         """Return a single-item array with the accepting state of the print queue.
 
         states: idle = [3], printing a job = [4], stopped = [5]
         """
         printer = self.printers.get(self.printer_name, {})
         state = printer.get("printer-state")
-        if not state:
+        if not state or state in [4, 5]:
-            return []
+            return b"8"  # offline
-        return [state]
+        return b"0"  # online
 
-    def close(self):
+    def close(self) -> None:
         """Close CUPS connection.
 
         Send pending job to the printer if needed.

src/escpos/printer/dummy.py

@@ -7,6 +7,7 @@
 :copyright: Copyright (c) 2012-2023 Bashlinux and python-escpos
 :license: MIT
 """
+from typing import List
 
 from ..escpos import Escpos
 
@@ -39,25 +40,24 @@ class Dummy(Escpos):
         """
         return is_usable()
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args, **kwargs) -> None:
         """Init with empty output list."""
         Escpos.__init__(self, *args, **kwargs)
-        self._output_list = []
+        self._output_list: List[bytes] = []
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Print any command sent in raw format.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
         self._output_list.append(msg)
 
     @property
-    def output(self):
+    def output(self) -> bytes:
         """Get the data that was sent to this printer."""
         return b"".join(self._output_list)
 
-    def clear(self):
+    def clear(self) -> None:
         """Clear the buffer of the printer.
 
         This method can be called if you send the contents to a physical printer
@@ -65,6 +65,6 @@ class Dummy(Escpos):
         """
         del self._output_list[:]
 
-    def close(self):
+    def close(self) -> None:
         """Close not implemented for Dummy printer."""
         pass

src/escpos/printer/file.py

@@ -88,12 +88,12 @@ class File(Escpos):
         if self.device:
             self.device.flush()
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Print any command sent in raw format.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
+        assert self.device
         self.device.write(msg)
         if self.auto_flush:
             self.flush()

src/escpos/printer/lp.py

@@ -182,12 +182,13 @@ class LP(Escpos):
         if not self._is_closing:
             self.open(_close_opened=False)
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Write raw command(s) to the printer.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
+        assert self.device is not None
+        assert self.device.stdin is not None
         if self.device.stdin.writable():
             self.device.stdin.write(msg)
         else:

src/escpos/printer/network.py

@@ -110,16 +110,17 @@ class Network(Escpos):
                 return
         logging.info("Network printer enabled")
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Print any command sent in raw format.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
+        assert self.device
         self.device.sendall(msg)
 
-    def _read(self):
+    def _read(self) -> bytes:
         """Read data from the TCP socket."""
+        assert self.device
         return self.device.recv(16)
 
     def close(self) -> None:

src/escpos/printer/serial.py

@@ -155,16 +155,17 @@ class Serial(Escpos):
                 return
         logging.info("Serial printer enabled")
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Print any command sent in raw format.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
+        assert self.device
         self.device.write(msg)
 
-    def _read(self):
+    def _read(self) -> bytes:
         """Read the data buffer and return it to the caller."""
+        assert self.device
         return self.device.read(16)
 
     def close(self) -> None:

src/escpos/printer/usb.py

@@ -74,9 +74,9 @@ class Usb(Escpos):
 
     def __init__(
         self,
-        idVendor: str = "",
+        idVendor: Optional[int] = None,
-        idProduct: str = "",
+        idProduct: Optional[int] = None,
-        usb_args: Dict[str, str] = {},
+        usb_args: Dict[str, Union[str, int]] = {},
         timeout: Union[int, float] = 0,
         in_ep: int = 0x82,
         out_ep: int = 0x01,
@@ -181,16 +181,17 @@ class Usb(Escpos):
         except usb.core.USBError as e:
             logging.error("Could not set configuration: %s", str(e))
 
-    def _raw(self, msg):
+    def _raw(self, msg: bytes) -> None:
         """Print any command sent in raw format.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
+        assert self.device
         self.device.write(self.out_ep, msg, self.timeout)
 
-    def _read(self):
+    def _read(self) -> bytes:
         """Read a data buffer and return it to the caller."""
+        assert self.device
         return self.device.read(self.in_ep, 16)
 
     @dependency_usb

src/escpos/printer/win32raw.py

@@ -76,7 +76,7 @@ class Win32Raw(Escpos):
         return is_usable()
 
     @dependency_win32print
-    def __init__(self, printer_name: str = "", *args, **kwargs):
+    def __init__(self, printer_name: str = "", *args, **kwargs) -> None:
         """Initialize default printer."""
         Escpos.__init__(self, *args, **kwargs)
         self.printer_name = printer_name
@@ -148,14 +148,17 @@ class Win32Raw(Escpos):
         win32print.ClosePrinter(self._device)
         self._device = False
 
-    def _raw(self, msg) -> None:
+    def _raw(self, msg: bytes) -> None:
         """Print any command sent in raw format.
 
         :param msg: arbitrary code to be printed
-        :type msg: bytes
         """
         if self.printer_name is None:
             raise DeviceNotFoundError("Printer not found")
         if not self.device:
             raise DeviceNotFoundError("Printer job not opened")
-        win32print.WritePrinter(self.device, msg)
+        win32print.WritePrinter(self.device, msg)  # type: ignore
+
+        # there is a bug in the typeshed
+        # https://github.com/mhammond/pywin32/blob/main/win32/src/win32print/win32print.cpp#L976
+        # https://github.com/python/typeshed/blob/main/stubs/pywin32/win32/win32print.pyi#L27C4-L27C4

test/test_cli.py

@@ -7,7 +7,6 @@ import os
 import shutil
 import tempfile
 
-import pytest
 from scripttest import TestFileEnvironment as TFE
 
 import escpos
@@ -31,22 +30,19 @@ class TestCLI:
     """Contains setups, teardowns, and tests for CLI"""
 
     @classmethod
-    def setup_class(cls):
+    def setup_class(cls) -> None:
         """Create a config file to read from"""
         with open(CONFIGFILE, "w") as config:
             config.write(CONFIG_YAML)
 
     @classmethod
-    def teardown_class(cls):
+    def teardown_class(cls) -> None:
         """Remove config file"""
         os.remove(CONFIGFILE)
         shutil.rmtree(TEST_DIR)
 
-    def setup_method(self):
+    def setup_method(self) -> None:
         """Create a file to print to and set up env"""
-        self.env = None
-        self.default_args = None
-
         self.env = TFE(
             base_path=TEST_DIR,
             cwd=os.getcwd(),
@@ -64,24 +60,24 @@ class TestCLI:
         finally:
             fhandle.close()
 
-    def teardown_method(self):
+    def teardown_method(self) -> None:
         """Destroy printer file and env"""
         os.remove(DEVFILE)
         self.env.clear()
 
-    def test_cli_help(self):
+    def test_cli_help(self) -> None:
         """Test getting help from cli"""
         result = self.env.run("python-escpos", "-h")
         assert not result.stderr
         assert "usage" in result.stdout
 
-    def test_cli_version(self):
+    def test_cli_version(self) -> None:
         """Test the version string"""
         result = self.env.run("python-escpos", "version")
         assert not result.stderr
         assert escpos.__version__ == result.stdout.strip()
 
-    def test_cli_version_extended(self):
+    def test_cli_version_extended(self) -> None:
         """Test the extended version information"""
         result = self.env.run("python-escpos", "version_extended")
         assert not result.stderr
@@ -89,7 +85,7 @@ class TestCLI:
         # test that additional information on e.g. Serial is printed
         assert "Serial" in result.stdout
 
-    def test_cli_text(self):
+    def test_cli_text(self) -> None:
         """Make sure text returns what we sent it"""
         test_text = "this is some text"
         result = self.env.run(
@@ -108,7 +104,7 @@ class TestCLI:
             result.files_updated[DEVFILE_NAME].bytes == "\x1bt\x00" + test_text + "\n"
         )
 
-    def test_cli_text_invalid_args(self):
+    def test_cli_text_invalid_args(self) -> None:
         """Test a failure to send valid arguments"""
         result = self.env.run(
             *(self.default_args + ("text", "--invalid-param", "some data")),

test/test_function_buzzer.py

@@ -1,14 +1,13 @@
 import pytest
-import six
 
 from escpos import printer
 from escpos.constants import BUZZER
 
 
-def test_buzzer_function_with_default_params():
+def test_buzzer_function_with_default_params() -> None:
     instance = printer.Dummy()
     instance.buzzer()
-    expected = BUZZER + six.int2byte(2) + six.int2byte(4)
+    expected = BUZZER + bytes((2, 4))
     assert instance.output == expected
 
 
@@ -26,10 +25,10 @@ def test_buzzer_function_with_default_params():
         [9, 9],
     ],
 )
-def test_buzzer_function(times, duration):
+def test_buzzer_function(times: int, duration: int) -> None:
     instance = printer.Dummy()
     instance.buzzer(times, duration)
-    expected = BUZZER + six.int2byte(times) + six.int2byte(duration)
+    expected = BUZZER + bytes((times, duration))
     assert instance.output == expected
 
 
@@ -46,7 +45,9 @@ def test_buzzer_function(times, duration):
         [3, 11, "duration must be between 1 and 9"],
     ],
 )
-def test_buzzer_fuction_with_outrange_values(times, duration, expected_message):
+def test_buzzer_fuction_with_outrange_values(
+    times: int, duration: int, expected_message: str
+) -> None:
     instance = printer.Dummy()
     with pytest.raises(ValueError) as e:
         instance.buzzer(times, duration)

test/test_function_cut.py

@@ -1,5 +1,3 @@
-import six
-
 import escpos.printer as printer
 from escpos.constants import GS
 
@@ -8,5 +6,5 @@ def test_cut_without_feed():
     """Test cut without feeding paper"""
     instance = printer.Dummy()
     instance.cut(feed=False)
-    expected = GS + b"V" + six.int2byte(66) + b"\x00"
+    expected = GS + b"V" + bytes((66,)) + b"\x00"
     assert instance.output == expected

test/test_function_image.py

@@ -16,7 +16,7 @@ from escpos.exceptions import ImageWidthError
 
 
 # Raster format print
-def test_bit_image_black():
+def test_bit_image_black() -> None:
     """
     Test printing solid black bit image (raster)
     """
@@ -30,7 +30,7 @@ def test_bit_image_black():
     assert instance.output == b"\x1dv0\x00\x01\x00\x01\x00\x80"
 
 
-def test_bit_image_white():
+def test_bit_image_white() -> None:
     """
     Test printing solid white bit image (raster)
     """
@@ -39,7 +39,7 @@ def test_bit_image_white():
     assert instance.output == b"\x1dv0\x00\x01\x00\x01\x00\x00"
 
 
-def test_bit_image_both():
+def test_bit_image_both() -> None:
     """
     Test printing black/white bit image (raster)
     """
@@ -58,7 +58,7 @@ def test_bit_image_transparent():
 
 
 # Column format print
-def test_bit_image_colfmt_black():
+def test_bit_image_colfmt_black() -> None:
     """
     Test printing solid black bit image (column format)
     """
@@ -67,7 +67,7 @@ def test_bit_image_colfmt_black():
     assert instance.output == b"\x1b3\x10\x1b*!\x01\x00\x80\x00\x00\x0a\x1b2"
 
 
-def test_bit_image_colfmt_white():
+def test_bit_image_colfmt_white() -> None:
     """
     Test printing solid white bit image (column format)
     """
@@ -76,7 +76,7 @@ def test_bit_image_colfmt_white():
     assert instance.output == b"\x1b3\x10\x1b*!\x01\x00\x00\x00\x00\x0a\x1b2"
 
 
-def test_bit_image_colfmt_both():
+def test_bit_image_colfmt_both() -> None:
     """
     Test printing black/white bit image (column format)
     """
@@ -87,7 +87,7 @@ def test_bit_image_colfmt_both():
     )
 
 
-def test_bit_image_colfmt_transparent():
+def test_bit_image_colfmt_transparent() -> None:
     """
     Test printing black/transparent bit image (column format)
     """
@@ -99,7 +99,7 @@ def test_bit_image_colfmt_transparent():
 
 
 # Graphics print
-def test_graphics_black():
+def test_graphics_black() -> None:
     """
     Test printing solid black graphics
     """
@@ -111,7 +111,7 @@ def test_graphics_black():
     )
 
 
-def test_graphics_white():
+def test_graphics_white() -> None:
     """
     Test printing solid white graphics
     """
@@ -123,7 +123,7 @@ def test_graphics_white():
     )
 
 
-def test_graphics_both():
+def test_graphics_both() -> None:
     """
     Test printing black/white graphics
     """
@@ -135,7 +135,7 @@ def test_graphics_both():
     )
 
 
-def test_graphics_transparent():
+def test_graphics_transparent() -> None:
     """
     Test printing black/transparent graphics
     """
@@ -147,7 +147,7 @@ def test_graphics_transparent():
     )
 
 
-def test_large_graphics():
+def test_large_graphics() -> None:
     """
     Test whether 'large' graphics that induce a fragmentation are handled correctly.
     """
@@ -162,13 +162,13 @@ def test_large_graphics():
 
 
 @pytest.fixture
-def dummy_with_width():
+def dummy_with_width() -> printer.Dummy:
     instance = printer.Dummy()
     instance.profile.profile_data = {"media": {"width": {"pixels": 384}}}
     return instance
 
 
-def test_width_too_large(dummy_with_width):
+def test_width_too_large(dummy_with_width: printer.Dummy) -> None:
     """
     Test printing an image that is too large in width.
     """
@@ -180,7 +180,7 @@ def test_width_too_large(dummy_with_width):
     instance.image(Image.new("RGB", (384, 200)))
 
 
-def test_center_image(dummy_with_width):
+def test_center_image(dummy_with_width: printer.Dummy) -> None:
     instance = dummy_with_width
 
     with pytest.raises(ImageWidthError):

test/test_function_linedisplay.py

@@ -11,21 +11,21 @@
 import escpos.printer as printer
 
 
-def test_function_linedisplay_select_on():
+def test_function_linedisplay_select_on() -> None:
     """test the linedisplay_select function (activate)"""
     instance = printer.Dummy()
     instance.linedisplay_select(select_display=True)
     assert instance.output == b"\x1B\x3D\x02"
 
 
-def test_function_linedisplay_select_off():
+def test_function_linedisplay_select_off() -> None:
     """test the linedisplay_select function (deactivate)"""
     instance = printer.Dummy()
     instance.linedisplay_select(select_display=False)
     assert instance.output == b"\x1B\x3D\x01"
 
 
-def test_function_linedisplay_clear():
+def test_function_linedisplay_clear() -> None:
     """test the linedisplay_clear function"""
     instance = printer.Dummy()
     instance.linedisplay_clear()

test/test_function_set.py

@@ -1,3 +1,5 @@
+from typing import Optional
+
 import pytest
 import six
 
@@ -6,7 +8,7 @@ from escpos.constants import SET_FONT, TXT_NORMAL, TXT_SIZE, TXT_STYLE
 from escpos.exceptions import SetVariableError
 
 
-def test_default_values_with_default():
+def test_default_values_with_default() -> None:
     """Default test, please copy and paste this block to test set method calls"""
     instance = printer.Dummy()
     instance.set_with_default()
@@ -26,7 +28,7 @@ def test_default_values_with_default():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_default_values():
+def test_default_values() -> None:
     """Default test"""
     instance = printer.Dummy()
     instance.set()
@@ -37,7 +39,7 @@ def test_default_values():
 # Size tests
 
 
-def test_set_size_2h():
+def test_set_size_2h() -> None:
     instance = printer.Dummy()
     instance.set_with_default(double_height=True)
 
@@ -56,7 +58,7 @@ def test_set_size_2h():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_size_2h_no_default():
+def test_set_size_2h_no_default() -> None:
     instance = printer.Dummy()
     instance.set(double_height=True)
 
@@ -68,7 +70,7 @@ def test_set_size_2h_no_default():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_size_2w():
+def test_set_size_2w() -> None:
     instance = printer.Dummy()
     instance.set_with_default(double_width=True)
 
@@ -87,7 +89,7 @@ def test_set_size_2w():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_size_2w_no_default():
+def test_set_size_2w_no_default() -> None:
     instance = printer.Dummy()
     instance.set(double_width=True)
 
@@ -99,7 +101,7 @@ def test_set_size_2w_no_default():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_size_2x():
+def test_set_size_2x() -> None:
     instance = printer.Dummy()
     instance.set_with_default(double_height=True, double_width=True)
 
@@ -118,7 +120,7 @@ def test_set_size_2x():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_size_2x_no_default():
+def test_set_size_2x_no_default() -> None:
     instance = printer.Dummy()
     instance.set(double_width=True, double_height=True)
 
@@ -130,7 +132,7 @@ def test_set_size_2x_no_default():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_size_custom():
+def test_set_size_custom() -> None:
     instance = printer.Dummy()
     instance.set_with_default(custom_size=True, width=8, height=7)
 
@@ -151,7 +153,7 @@ def test_set_size_custom():
 
 @pytest.mark.parametrize("width", [1, 8])
 @pytest.mark.parametrize("height", [1, 8])
-def test_set_size_custom_no_default(width, height):
+def test_set_size_custom_no_default(width: int, height: int) -> None:
     instance = printer.Dummy()
     instance.set(custom_size=True, width=width, height=height)
 
@@ -165,7 +167,9 @@ def test_set_size_custom_no_default(width, height):
 
 @pytest.mark.parametrize("width", [None, 0, 9, 10, 4444])
 @pytest.mark.parametrize("height", [None, 0, 9, 10, 4444])
-def test_set_size_custom_invalid_input(width, height):
+def test_set_size_custom_invalid_input(
+    width: Optional[int], height: Optional[int]
+) -> None:
     instance = printer.Dummy()
     with pytest.raises(SetVariableError):
         instance.set(custom_size=True, width=width, height=height)
@@ -174,7 +178,7 @@ def test_set_size_custom_invalid_input(width, height):
 # Flip
 
 
-def test_set_flip():
+def test_set_flip() -> None:
     instance = printer.Dummy()
     instance.set_with_default(flip=True)
 
@@ -193,7 +197,7 @@ def test_set_flip():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_flip_no_default():
+def test_set_flip_no_default() -> None:
     instance = printer.Dummy()
     instance.set(flip=True)
 
@@ -205,7 +209,7 @@ def test_set_flip_no_default():
 # Smooth
 
 
-def test_smooth():
+def test_smooth() -> None:
     instance = printer.Dummy()
     instance.set_with_default(smooth=True)
 
@@ -227,7 +231,7 @@ def test_smooth():
 # Type
 
 
-def test_set_bold():
+def test_set_bold() -> None:
     instance = printer.Dummy()
     instance.set_with_default(bold=True)
 
@@ -246,7 +250,7 @@ def test_set_bold():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_underline():
+def test_set_underline() -> None:
     instance = printer.Dummy()
     instance.set_with_default(underline=1)
 
@@ -265,7 +269,7 @@ def test_set_underline():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_set_underline2():
+def test_set_underline2() -> None:
     instance = printer.Dummy()
     instance.set_with_default(underline=2)
 
@@ -287,7 +291,7 @@ def test_set_underline2():
 # Align
 
 
-def test_align_center():
+def test_align_center() -> None:
     instance = printer.Dummy()
     instance.set_with_default(align="center")
 
@@ -306,7 +310,7 @@ def test_align_center():
     assert instance.output == b"".join(expected_sequence)
 
 
-def test_align_right():
+def test_align_right() -> None:
     instance = printer.Dummy()
     instance.set_with_default(align="right")
 
@@ -328,7 +332,7 @@ def test_align_right():
 # Densities
 
 
-def test_densities():
+def test_densities() -> None:
     for density in range(8):
         instance = printer.Dummy()
         instance.set_with_default(density=density)
@@ -352,7 +356,7 @@ def test_densities():
 # Invert
 
 
-def test_invert():
+def test_invert() -> None:
     instance = printer.Dummy()
     instance.set_with_default(invert=True)
 

test/test_function_text.py

@@ -10,8 +10,7 @@
 
 import hypothesis.strategies as st
 import mock
-import pytest
+from hypothesis import given
-from hypothesis import assume, given
 
 from escpos.printer import Dummy
 
@@ -21,7 +20,7 @@ def get_printer():
 
 
 @given(text=st.text())
-def test_text(text):
+def test_text(text: str) -> None:
     """Test that text() calls the MagicEncode object."""
     instance = get_printer()
     instance.magic.write = mock.Mock()
@@ -29,7 +28,7 @@ def test_text(text):
     instance.magic.write.assert_called_with(text)
 
 
-def test_block_text():
+def test_block_text() -> None:
     printer = get_printer()
     printer.block_text(
         "All the presidents men were eating falafel for breakfast.", font="a"
@@ -39,25 +38,25 @@ def test_block_text():
     )
 
 
-def test_textln():
+def test_textln() -> None:
     printer = get_printer()
     printer.textln("hello, world")
     assert printer.output == b"hello, world\n"
 
 
-def test_textln_empty():
+def test_textln_empty() -> None:
     printer = get_printer()
     printer.textln()
     assert printer.output == b"\n"
 
 
-def test_ln():
+def test_ln() -> None:
     printer = get_printer()
     printer.ln()
     assert printer.output == b"\n"
 
 
-def test_multiple_ln():
+def test_multiple_ln() -> None:
     printer = get_printer()
     printer.ln(3)
     assert printer.output == b"\n\n\n"

test/test_image.py

@@ -7,11 +7,12 @@ converted to ESC/POS column & raster formats.
 :copyright: Copyright (c) 2016 `Michael Billington <michael.billington@gmail.com>`_
 :license: MIT
 """
+from typing import List
 
 from escpos.image import EscposImage
 
 
-def test_image_black():
+def test_image_black() -> None:
     """
     Test rendering solid black image
     """
@@ -19,7 +20,7 @@ def test_image_black():
         _load_and_check_img("canvas_black." + img_format, 1, 1, b"\x80", [b"\x80"])
 
 
-def test_image_black_transparent():
+def test_image_black_transparent() -> None:
     """
     Test rendering black/transparent image
     """
@@ -29,7 +30,7 @@ def test_image_black_transparent():
         )
 
 
-def test_image_black_white():
+def test_image_black_white() -> None:
     """
     Test rendering black/white image
     """
@@ -39,7 +40,7 @@ def test_image_black_white():
         )
 
 
-def test_image_white():
+def test_image_white() -> None:
     """
     Test rendering solid white image
     """
@@ -47,7 +48,7 @@ def test_image_white():
         _load_and_check_img("canvas_white." + img_format, 1, 1, b"\x00", [b"\x00"])
 
 
-def test_split():
+def test_split() -> None:
     """
     test whether the split-function works as expected
     """
@@ -62,12 +63,12 @@ def test_split():
 
 
 def _load_and_check_img(
-    filename,
+    filename: str,
-    width_expected,
+    width_expected: int,
-    height_expected,
+    height_expected: int,
-    raster_format_expected,
+    raster_format_expected: bytes,
-    column_format_expected,
+    column_format_expected: List[bytes],
-):
+) -> None:
     """
     Load an image, and test whether raster & column formatted output, sizes, etc match expectations.
     """

test/test_magicencode.py

@@ -13,7 +13,7 @@ import hypothesis.strategies as st
 import pytest
 from hypothesis import example, given
 
-from escpos.exceptions import CharCodeError, Error
+from escpos.exceptions import Error
 from escpos.katakana import encode_katakana
 from escpos.magicencode import Encoder, MagicEncode
 
@@ -23,23 +23,23 @@ class TestEncoder:
     Tests the single encoders.
     """
 
-    def test_can_encode(self):
+    def test_can_encode(self) -> None:
         assert not Encoder({"CP437": 1}).can_encode("CP437", "€")
         assert Encoder({"CP437": 1}).can_encode("CP437", "á")
         assert not Encoder({"foobar": 1}).can_encode("foobar", "a")
 
-    def test_find_suitable_encoding(self):
+    def test_find_suitable_encoding(self) -> None:
         assert not Encoder({"CP437": 1}).find_suitable_encoding("€")
         assert Encoder({"CP858": 1}).find_suitable_encoding("€") == "CP858"
 
-    def test_find_suitable_encoding_unnecessary_codepage_swap(self):
+    def test_find_suitable_encoding_unnecessary_codepage_swap(self) -> None:
         enc = Encoder({"CP857": 1, "CP437": 2, "CP1252": 3, "CP852": 4, "CP858": 5})
         # desired behavior would be that the encoder always stays in the lower
         # available codepages if possible
         for character in ("Á", "É", "Í", "Ó", "Ú"):
             assert enc.find_suitable_encoding(character) == "CP857"
 
-    def test_get_encoding(self):
+    def test_get_encoding(self) -> None:
         with pytest.raises(ValueError):
             Encoder({}).get_encoding_name("latin1")
 
@@ -122,9 +122,9 @@ class TestKatakana:
     @example("カタカナ")
     @example("あいうえお")
     @example("ﾊﾝｶｸｶﾀｶﾅ")
-    def test_accept(self, text):
+    def test_accept(self, text: str) -> None:
         encode_katakana(text)
 
-    def test_result(self):
+    def test_result(self) -> None:
         assert encode_katakana("カタカナ") == b"\xb6\xc0\xb6\xc5"
         assert encode_katakana("あいうえお") == b"\xb1\xb2\xb3\xb4\xb5"

test/test_printers/test_printer_cups.py

@@ -19,7 +19,7 @@ pytestmark = pytest.mark.skipif(
 )
 
 
-def test_device_not_initialized(cupsprinter):
+def test_device_not_initialized(cupsprinter) -> None:
     """
     GIVEN a cups printer object
     WHEN it is not initialized
@@ -28,7 +28,7 @@ def test_device_not_initialized(cupsprinter):
     assert cupsprinter._device is False
 
 
-def test_open_raise_exception(cupsprinter, devicenotfounderror):
+def test_open_raise_exception(cupsprinter, devicenotfounderror) -> None:
     """
     GIVEN a cups printer object
     WHEN open() is set to raise a DeviceNotFoundError on error
@@ -40,7 +40,7 @@ def test_open_raise_exception(cupsprinter, devicenotfounderror):
         cupsprinter.open(raise_not_found=True)
 
 
-def test_open_not_raise_exception(cupsprinter, caplog):
+def test_open_not_raise_exception(cupsprinter, caplog) -> None:
     """
     GIVEN a cups printer object
     WHEN open() is set to not raise on error but simply cancel
@@ -55,7 +55,7 @@ def test_open_not_raise_exception(cupsprinter, caplog):
     assert cupsprinter.device is None
 
 
-def test_open(cupsprinter, caplog, mocker):
+def test_open(cupsprinter, caplog, mocker) -> None:
     """
     GIVEN a cups printer object and a mocked pycups device
     WHEN a valid connection to a device is opened
@@ -74,7 +74,7 @@ def test_open(cupsprinter, caplog, mocker):
     assert cupsprinter.device
 
 
-def test_close_on_reopen(cupsprinter, mocker):
+def test_close_on_reopen(cupsprinter, mocker) -> None:
     """
     GIVEN a cups printer object and a mocked connection
     WHEN a valid connection to a device is reopened before close
@@ -112,7 +112,7 @@ def test_close(cupsprinter, caplog, mocker):
     assert cupsprinter._device is False
 
 
-def test_send_on_close(cupsprinter, mocker):
+def test_send_on_close(cupsprinter, mocker) -> None:
     """
     GIVEN a cups printer object and a mocked pycups device
     WHEN closing connection before send the buffer
@@ -133,7 +133,7 @@ def test_send_on_close(cupsprinter, mocker):
     assert cupsprinter.pending_job is False
 
 
-def test_raw_raise_exception(cupsprinter):
+def test_raw_raise_exception(cupsprinter) -> None:
     """
     GIVEN a cups printer object
     WHEN passing a non byte string to _raw()
@@ -145,7 +145,7 @@ def test_raw_raise_exception(cupsprinter):
     assert cupsprinter.pending_job is False
 
 
-def test_raw(cupsprinter):
+def test_raw(cupsprinter) -> None:
     """
     GIVEN a cups printer object
     WHEN passing a byte string to _raw()
@@ -156,7 +156,7 @@ def test_raw(cupsprinter):
     assert cupsprinter.tmpfile.read() == b"Test"
 
 
-def test_printers_no_device(cupsprinter):
+def test_printers_no_device(cupsprinter) -> None:
     """
     GIVEN a cups printer object
     WHEN device is None
@@ -166,11 +166,11 @@ def test_printers_no_device(cupsprinter):
     assert cupsprinter.printers == {}
 
 
-def test_read_no_device(cupsprinter):
+def test_read_no_device(cupsprinter) -> None:
     """
     GIVEN a cups printer object
     WHEN device is None
-    THEN check the return value is []
+    THEN check the return value is b'8'
     """
     cupsprinter.device = None
-    assert cupsprinter._read() == []
+    assert cupsprinter._read() == b"8"

tox.ini

@@ -58,6 +58,7 @@ deps = mypy
        types-Pillow
        types-pyserial
        types-pywin32>=306.0.0.6
+       types-flask
        hypothesis>=6.83
        jaconv
-commands = mypy src test
+commands = mypy src test examples