# Charex - Enhance Numba with NumPy's string operations

**URL:** <https://numba.discourse.group/t/charex-enhance-numba-with-numpys-string-operations/2419>\
**Category:** Showcase\
**Created:** [February 23, 2024, 10:45pm UTC](https://numba.discourse.group/t/charex-enhance-numba-with-numpys-string-operations/2419 "2024-02-23T22:45:23Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![nmehran](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/nmehran/32/997_2.png) [@nmehran](https://numba.discourse.group/u/nmehran)\
**Post date:** [February 23, 2024, 10:45pm UTC](https://numba.discourse.group/t/charex-enhance-numba-with-numpys-string-operations/2419/1 "2024-02-23T22:45:23Z")

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I present a project potentially useful for the Numba ecosystem: [charex](https://github.com/nmehran/charex/). This package is designed to extend Numba’s capabilities by integrating NumPy’s string operations within Numba-optimized functions.

### Overview

`charex` stands for “Character Extensions” and enables Numba access to the suite of string comparison operations and occurrence and property methods available in NumPy’s `char` module:

```python
import charex

```

For those interested in trying out charex, you can find the package and more details on GitHub at the charex repository. The benchmarks and tests are also available within the repository, providing insights into the package’s performance.

### Comparison operations:

- `char.equal`
- `char.not_equal`
- `char.greater_equal`
- `char.less_equal`
- `char.greater`
- `char.less`
- `char.compare_chararrays`

### Occurrence and Property information:

- `char.count`
- `char.endswith`
- `char.startswith`
- `char.find`
- `char.rfind`
- `char.index`
- `char.rindex`
- `char.str_len`
- `char.isalpha`
- `char.isalnum`
- `char.isspace`
- `char.isdecimal`
- `char.isdigit`
- `char.isnumeric`
- `char.istitle`
- `char.isupper`
- `char.islower`

### Further Information

I’ve tested charex to ensure compatibility and performance, with the latest tests conducted using Numba 0.59.0 and NumPy 1.26.3. Please feel free to contribute, validate, provide feedback, and discuss how charex can be further improved. The aim is to gather feedback and further refine the project for integration into Numba (see: [#8500](https://github.com/numba/numba/pull/8500)).

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**Author:** ![Oyibo](https://avatars.discourse-cdn.com/v4/letter/o/4af34b/32.png) [@Oyibo](https://numba.discourse.group/u/Oyibo)\
**Post date:** [February 24, 2024, 9:25pm UTC](https://numba.discourse.group/t/charex-enhance-numba-with-numpys-string-operations/2419/2 "2024-02-24T21:25:28Z")

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Kudos to you, @nmehran , for introducing charex, a great extension that enhances Numba’s capabilities with NumPy string operations.

Charex currently aligns with the existing NumPy “char” namespace. As outlined in NEP-55, NumPy will slowly transition from “char” to “strings” namespace. Its introduction may already be imminent in NumPy 2.0. The timing might be a bit unfortunate.

Thank you for your valuable contribution.

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**Author:** ![nmehran](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/nmehran/32/997_2.png) [@nmehran](https://numba.discourse.group/u/nmehran)\
**Post date:** [February 26, 2024, 7:43pm UTC](https://numba.discourse.group/t/charex-enhance-numba-with-numpys-string-operations/2419/3 "2024-02-26T19:43:28Z")

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Hi @Oyibo , I appreciate your insight with regard to NEP-55.

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**Author:** ![nmehran](https://yyz2.discourse-cdn.com/free1/user_avatar/numba.discourse.group/nmehran/32/997_2.png) [@nmehran](https://numba.discourse.group/u/nmehran)\
**Post date:** [June 1, 2026, 3:11pm UTC](https://numba.discourse.group/t/charex-enhance-numba-with-numpys-string-operations/2419/4 "2026-06-01T15:11:00Z")

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Quick update, roughly two years later: charex has now been refreshed for the current Numba / NumPy string landscape.

The short version: the NEP-55 / `np.strings` concern that @Oyibo raised was exactly right. As of `charex` 0.5.0, the project is no longer limited to NumPy’s `np.char` namespace.

Release: [Release charex 0.5.0 · nmehran/charex · GitHub](https://github.com/nmehran/charex/releases/tag/v0.5.0)

Notable changes since the original 2024 version:

- Updated compatibility to Numba `0.65.1`, llvmlite `0.47.x`, Python `3.10-<3.15`.
- Supports NumPy `1.22-<1.27` and `2.0-<2.5`.
- Keeps `np.char` support for fixed-width `S` / `U` arrays.
- Adds `np.strings` support for fixed-width `S` / `U`.
- Adds NumPy 2.x `StringDType` support through `np.strings`, including variable-width strings and `na_object` variants.
- Extends the read-only catalog to scalar, 0-D, 1-D, N-D, strided, reversed, read-only, zero-stride, empty, and broadcast-compatible shapes.
- Preserves the semantic differences between `np.char` and `np.strings`, especially around trailing whitespace / NUL behavior.

The supported read-only catalog now includes comparisons, occurrence/search operations, `str_len`, predicates, and `np.char.compare_chararrays`.

A full shape/behavior audit currently reports:

- `1702` audit rows
- `1702` matching rows
- `0` mismatches
- `0` NumPy-accepted cases rejected by charex

The current benchmark matrix covers 135 fixed-width and `StringDType` cases on Python 3.12.8, NumPy 2.4.6, Numba 0.65.1, and llvmlite 0.47.0. In that matrix, charex ranges from `1.02x` to `6.51x` NumPy speed, with a `1.60x` median.

Still out of scope for now (feasible): transformation operations such as replace, case conversion, strip, pad, join, split, encode, and decode.

The project is much closer to the original goal now: a focused compatibility and performance layer for NumPy string operations in Numba, while also keeping the implementation and audit results available for official Numba string-support integration.