Unicode grapheme helpers
A Python package for working with user perceived characters. More specifically,
string manipulation and calculation functions for working with grapheme cluster
groups (graphemes) as defined by the Unicode Standard Annex #29 <http://unicode.org/reports/tr29/>
_.
documentation <https://grapheme.readthedocs.io/>
_
.. code-block:: console
pip install grapheme
The currently supported version of Unicode: 13.0.0.
Unicode strings are made up of a series of unicode characters, but a unicode character does not always map to a user perceived character. Some human perceived characters are represented as two or more unicode characters.
However, all built in python string functions and string methods work with single unicode characters without considering their connection to each other.
.. code-block:: python
>>> string = 'u̲n̲d̲e̲r̲l̲i̲n̲e̲d̲'
>>> len(string)
20
>>> grapheme.length(string)
10
>>> string[:3]
'u̲n'
>>> grapheme.substr(string, 0, 3)
'u̲n̲d̲'
This library implements the unicode default rules for extended grapheme clusters, and provides a set of functions for string manipulation based on graphemes.
See <https://grapheme.readthedocs.io/en/latest/>
_.
You should consider working with graphemes over unicode code points when:
You should work with normal python string functions when:
Calculating graphemes require traversing the string and checking each character against a set of rules and the previous character(s). Because of this, all functions in this module will scale linearly to the string length.
Whenever possible, they will only traverse the string for as long as needed and return
early as soon as the requested output is generated. For example, the grapheme.slice
function only has to traverse the string until the last requested grapheme is found, and
does not care about the rest of the string.
You should probably only use this package for testing/manipulating fairly short strings or with the beginning of long strings.
When testing with a string of 10 000 ascii characters, and a 3.1 GHz processor, the execution time for some possible calls is roughly:
================================================================ ==========================
Code Approximate execution time
================================================================ ==========================
len(long_ascii_string)
8.1e-10 seconds
grapheme.length(long_ascii_string)
1.5e-04 seconds
grapheme.length(long_ascii_string, 500)
8.7e-06 seconds
long_ascii_string[0:100]
1.3e-09 seconds
grapheme.slice(long_ascii_string, 0, 100)
2.5e-06 seconds
long_ascii_string[:100] in long_ascii_string
4.0e-09 seconds
grapheme.contains(long_ascii_string, long_ascii_string[:100])
3.9e-06 seconds
long_ascii_string[-100:] in long_ascii_string
2.1e-07 seconds
grapheme.contains(long_ascii_string, long_ascii_string[-100:])
1.9e-04 seconds
================================================================ ==========================
Execution times may improve in later releases, but calculating graphemes is and will continue to be notably slower than just counting unicode code points.
This is not a complete list, but a some examples of when graphemes use multiple characters:
If you wish to contribute or edit this package, create a fork and clone it.
Then install in locally editable (-e
) mode and run the tests.
.. code-block:: console
pip install -e .[test]
py.test
The library will issue a new release for each new unicode version.
The steps necessary for this:
Annex #29 <http://unicode.org/reports/tr29/>
_ (see modifications).data files <http://www.unicode.org/Public/>
_ from unicode into the unicode-data folder.
For the given version, some are in ucd
and some are in ucd/auxiliary
.make process-data-files
to parse those files (will update the
grapheme_break_property.json
file).