Introduction
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.
Installation
The stable version of this package is maintained on pypi, install using pip:
pip install wcwidth
Example
Problem: given the following phrase (Japanese),
>>> text = u'コンニチハ'
Python incorrectly uses the string length of 5 codepoints rather than the printible 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
Choosing a Version
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.
wcwidth, wcswidth
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
Indeterminate (not printable).
- 0
Does not advance the cursor, such as NULL or Combining.
- 2
Characters of category East Asian Wide (W) or East Asian Full-width (F) which are displayed using two terminal cells.
- 1
All others.
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
Developing
Install wcwidth in editable mode:
pip install -e .
Execute unit tests using tox:
tox -e py27,py35,py36,py37,py38,py39,py310,py311,py312
Updating Unicode Version
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.
Building Documentation
This project is using sphinx 4.5 to build documentation:
tox -e sphinx
The output will be in docs/_build/html/.
Updating Requirements
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
Utilities
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
Uses
This library is used in:
jquast/blessed: a thin, practical wrapper around terminal capabilities in Python.
prompt-toolkit/python-prompt-toolkit: a Library for building powerful interactive command lines in Python.
dbcli/pgcli: Postgres CLI with autocompletion and syntax highlighting.
thomasballinger/curtsies: a Curses-like terminal wrapper with a display based on compositing 2d arrays of text.
selectel/pyte: Simple VTXXX-compatible linux terminal emulator.
astanin/python-tabulate: Pretty-print tabular data in Python, a library and a command-line utility.
rspeer/python-ftfy: Fixes mojibake and other glitches in Unicode text.
nbedos/termtosvg: Terminal recorder that renders sessions as SVG animations.
peterbrittain/asciimatics: Package to help people create full-screen text UIs.
python-cmd2/cmd2: A tool for building interactive command line apps
stratis-storage/stratis-cli: CLI for the Stratis project
ihabunek/toot: A Mastodon CLI/TUI client
saulpw/visidata: Terminal spreadsheet multitool for discovering and arranging data
Other Languages
timoxley/wcwidth: JavaScript
Text::CharWidth: Perl
bluebear94/Terminal-WCWidth: Perl 6
grepsuzette/wcwidth: Haxe
aperezdc/lua-wcwidth: Lua
fumiyas/wcwidth-cjk: LD_PRELOAD override
joshuarubin/wcwidth9: Unicode version 9 in C
History
- 0.2.7 2023-09-28
Updated tables to include Unicode Specification 15.1.0.
- 0.2.6 2023-01-14
Updated tables to include Unicode Specification 14.0.0 and 15.0.0.
Changed developer tools to use pip-compile, and to use jinja2 templates for code generation in bin/update-tables.py to prepare for possible compiler optimization release.
- 0.2.1 .. 0.2.5 2020-06-23
Repository changes to update tests and packaging issues, and begin tagging repository with matching release versions.
- 0.2.0 2020-06-01
Enhancement: Unicode version may be selected by exporting the Environment variable UNICODE_VERSION, such as 13.0, or 6.3.0. See the jquast/ucs-detect CLI utility for automatic detection.
Enhancement: API Documentation is published to readthedocs.org.
Updated tables for all Unicode Specifications with files published in a programmatically consumable format, versions 4.1.0 through 13.0
- 0.1.9 2020-03-22
Performance optimization by Avram Lubkin, PR #35.
Updated tables to Unicode Specification 13.0.0.
- 0.1.8 2020-01-01
Updated tables to Unicode Specification 12.0.0. (PR #30).
- 0.1.7 2016-07-01
Updated tables to Unicode Specification 9.0.0. (PR #18).
- 0.1.6 2016-01-08 Production/Stable
LICENSE file now included with distribution.
- 0.1.5 2015-09-13 Alpha
Bugfix: Resolution of “combining character width” issue, most especially those that previously returned -1 now often (correctly) return 0. resolved by Philip Craig via PR #11.
Deprecated: The module path wcwidth.table_comb is no longer available, it has been superseded by module path wcwidth.table_zero.
- 0.1.4 2014-11-20 Pre-Alpha
Feature: 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).
Feature: added static analysis (prospector) to testing framework.
- 0.1.3 2014-10-29 Pre-Alpha
Bugfix: 2nd parameter of wcswidth was not honored. (Thomas Ballinger, PR #4).
- 0.1.2 2014-10-28 Pre-Alpha
Updated tables to Unicode Specification 7.0.0. (Thomas Ballinger, PR #3).
- 0.1.1 2014-05-14 Pre-Alpha
Initial release to pypi, Based on Unicode Specification 6.3.0
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.
1 maintainer
Metadata
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Release files for wcwidth 0.2.7
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