This library is mainly for CLI programs that carefully produce output for Terminals, or make pretend to be an emulator.
Problem Statement: The printable length of most strings are equal to the number of cells they occupy on the screen 1 character : 1 cell. However, there are categories of characters that occupy 2 cells (full-wide), and others that occupy 0 cells (zero-width).
Solution: POSIX.1-2001 and POSIX.1-2008 conforming systems provide wcwidth(3) and wcswidth(3) C functions of which this python module's functions precisely copy. These functions return the number of cells a unicode string is expected to occupy.
The stable version of this package is maintained on pypi, install using pip:
pip install wcwidth
Problem: given the following phrase (Japanese),
Python incorrectly uses the string length of 5 codepoints rather than the printable length of 10 cells, so that when using the rjust function, the output length is wrong:
>>> print(len('コンニチハ'))
5
>>> print('コンニチハ'.rjust(20, '_'))
_______________コンニチハ
By defining our own "rjust" function that uses wcwidth, we can correct this:
>>> def wc_rjust(text, length, padding=' '): ... from wcwidth import wcswidth ... return padding * max(0, (length - wcswidth(text))) + text ...
Our Solution uses wcswidth to determine the string length correctly:
>>> from wcwidth import wcswidth
>>> print(wcswidth('コンニチハ'))
10
>>> print(wc_rjust('コンニチハ', 20, '_'))
__________コンニチハ
Export an environment variable, UNICODE_VERSION. This should be done by terminal emulators or those developers experimenting with authoring one of their own, from shell:
$ export UNICODE_VERSION=13.0
If unspecified, the latest version is used. If your Terminal Emulator does not export this variable, you can use the jquast/ucs-detect utility to automatically detect and export it to your shell.
Use function wcwidth() to determine the length of a single unicode character, and wcswidth() to determine the length of many, a string of unicode characters.
Briefly, return values of function wcwidth() are:
-1
0
2
1
Function wcswidth() simply returns the sum of all values for each character along a string, or -1 when it occurs anywhere along a string.
Full API Documentation at https://wcwidth.readthedocs.org
Install wcwidth in editable mode:
pip install -e .
Execute unit tests using tox:
tox -e py27,py35,py36,py37,py38,py39,py310,py311,py312
Regenerate python code tables from latest Unicode Specification data files:
tox -e update
The script is located at bin/update-tables.py, requires Python 3.9 or later. It is recommended but not necessary to run this script with the newest Python, because the newest Python has the latest unicodedata for generating comments.
This project is using sphinx 4.5 to build documentation:
tox -e sphinx
The output will be in docs/_build/html/.
This project is using pip-tools to manage requirements.
To upgrade requirements for updating unicode version, run:
tox -e update_requirements_update
To upgrade requirements for testing, run:
tox -e update_requirements37,update_requirements39
To upgrade requirements for building documentation, run:
tox -e update_requirements_docs
Supplementary tools for browsing and testing terminals for wide unicode characters are found in the bin/ of this project's source code. Just ensure to first pip install -r requirements-develop.txt from this projects main folder. For example, an interactive browser for testing:
python ./bin/wcwidth-browser.py
This library is used in:
bin, docs, and tox.ini in the source distributionUNICODE_VERSION, such as 13.0, or 6.3.0. See the jquast/ucs-detect CLI utility for automatic detection.LICENSE file now included with distribution.wcwidth.table_comb is no longer available, it has been superseded by module path wcwidth.table_zero.wcswidth() now determines printable length for (most) combining characters. The developer's tool bin/wcwidth-browser.py is improved to display combining characters when provided the --combining option (Thomas Ballinger and Leta Montopoli PR #5).This code was originally derived directly from C code of the same name, whose latest version is available at https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c:
* Markus Kuhn -- 2007-05-26 (Unicode 5.0) * * Permission to use, copy, modify, and distribute this software * for any purpose and without fee is hereby granted. The author * disclaims all warranties with regard to this software.
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