safeprint 0.2.0
A printer suppressing UnicodeEncodeError
License: MIT
Keywords: windows cmd unicode print

safeprint
=========

A printer suppressing UnicodeEncodeError.

Installation
------------

::

	pip install safeprint


Usage
-----

Basic:

::

	from safeprint import print

	print("你好世界！" "こんにちは世界" "안녕하세요세계")

Hook callback:

::

	import safeprint

	# create a printer
	printer = safeprint.Printer()

	def callback(text):
		# do something with the text

	printer.add_listener(callback)

	printer.print(1, 2, 3, sep=", ")

	printer.remove_listener(callback)

Note for python 2
-----------------

If you send a str object to the print function, safeprint will encode it into unicode object with utf-8 encoding.

How it works
------------

Python 3
~~~~~~~~

* Printing to the console

  Before printing, python encodes your text `based on the encoding of your console <https://docs.python.org/3/library/sys.html#sys.stdout>`__, which is usally "utf-8" in Linux. Under Windows, you can check your default code page with cmd command ``chcp``.

  As the result, if python can't encode your text with the encoding, "UnicodeEncodeError" is raised. You can solve this by switching console encoding - run command ``chcp 65001`` to switch to utf-8 before running python.

  What safeprint does, is to use `win-unicode-console <https://github.com/Drekin/win-unicode-console>`__, which uses WinAPI to write unicode string to the console.

  Also, after python 3.6, `python has builtin support for that <https://docs.python.org/3/whatsnew/3.6.html#pep-528-change-windows-console-encoding-to-utf-8>`__, so you don't need win-unicode-console anymore.

* Printing to a file (redirected output)

  This cause "UnicodeEncodeError" because python uses your system code page as default encoding for stdios. To solve it, you should set environment variable `"PYTHONIOENCODING" <https://docs.python.org/3/using/cmdline.html#envvar-PYTHONIOENCODING>`__ to "utf-8", which makes python use utf-8 as the encoding.

  What safeprint does is just always encode your text in utf-8, and write the bytes to stdout directly.

Python 2
~~~~~~~~

In python 2, there is no difference between bytes and str. An str is just a series of bytes, which is what python actually read from your source code. If you write the same string but save in different source file with different encoding, python will get different series of bytes too.

* Printing to the console

  Since there is no difference between bytes and str, writing str to console is just writing bytes to console and will never raise an UnicodeEncodeError. However, you might get garbled if the encoding of the console doesn't match the encoding of the source code (and python 2 just doesn't work well with cp65001, switching code page doesn't work).

  When printing unicode object, python will try to encode it into bytes with the encoding of the console like python 3, which might result in UnicodeEncodeError.

  The solution is same as in python 3. safeprint uses win-unicode-console to print unicode text.

* Printing to a file (redirected output)

  As we said, there is no difference between bytes and str. When printing a str to a file, is actually just writing a series of bytes to the file, which will never raise an UnicodeEncodeError.

  But, when printing an unicode object, python has to encode the unicode into bytes, based on the default encoding of python (you can check the default encoding by running this python script ``import sys; print(sys.getdefaultencoding())``, it defaults to "ascii" in python 2). As the result, the printing will fail with UnicodeEncodeError if python can't encode your unicode object.

  To solve this, you can set the environment variable "PYTHONIOENCODING", or encode your unicode object with utf-8 before sending it to the print function, which is what safeprint does.

Changelog
---------

* 0.2.0 (Mar 1, 2017)

  - Support Python 2.
  - Add printer for redirected output.
  - Drop EchoPrinter.

* 0.1.4 (Dec 31, 2016)

  - Make win-unicode-console optional with Python 3.6.

* 0.1.2 (Jul 21, 2016)

  - Compatible with win-unicode-console 0.5

* 0.1.1 (Apr 15, 2016)

  - Fix builtins bug.

* 0.1.0 (Apr 15, 2016)

  - Initial release.