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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 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

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:

Other Languages

History

0.2.13 2024-01-06
  • Bugfix zero-width support for Hangul Jamo (Korean)
0.2.12 2023-11-21
  • re-release to remove .pyi file misplaced in wheel files Issue #101.
0.2.11 2023-11-20
  • Include tests files in the source distribution (PR #98, PR #100).
0.2.10 2023-11-13
  • Bugfix accounting of some kinds of emoji sequences using U+FE0F Variation Selector 16 (PR #97).
  • Updated Specification.
0.2.9 2023-10-30
  • Bugfix zero-width characters used in Emoji ZWJ sequences, Balinese, Jamo, Devanagari, Tamil, Kannada and others (PR #91).
  • Updated to include Specification of character measurements.
0.2.8 2023-09-30
  • Include requirements files in the source distribution (PR #82).
0.2.7 2023-09-28
  • Updated tables to include Unicode Specification 15.1.0.
  • Include bin, docs, and tox.ini in the source distribution
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
0.1.3 2014-10-29 Pre-Alpha
0.1.2 2014-10-28 Pre-Alpha
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.