narwhals 0.9.0

Extremely lightweight compatibility layer between pandas, Polars, cuDF, and Modin

Narwhals

Extremely lightweight and extensible compatibility layer between Polars, pandas, Modin, and cuDF (and more!).

• Read the documentation
• Chat with us on Discord!

Seamlessly support all, without depending on any!

• ✅ Just use a subset of the Polars API, no need to learn anything new
• ✅ No dependencies (not even Polars), keep your library lightweight
• ✅ Separate lazy and eager APIs
• ✅ Use Expressions
• ✅ 100% branch coverage, tested against pandas and Polars nightly builds
• ✅ Preserve your Index (if present) without it getting in the way
• ✅ Zero 3rd party imports, Narwhals only uses what you already have

Used by

Join the party!

• scikit-lego
• scikit-playtime
• timebasedcv

Installation

pip install narwhals

Or just vendor it, it's only a bunch of pure-Python files.

Usage

There are three steps to writing dataframe-agnostic code using Narwhals:

1. use narwhals.from_native to wrap a pandas/Polars/Modin/cuDF DataFrame/LazyFrame in a Narwhals class

2. use the subset of the Polars API supported by Narwhals

3. use narwhals.to_native to return an object to the user in its original dataframe flavour. For example:

   • if you started with pandas, you'll get pandas back
   • if you started with Polars, you'll get Polars back
   • if you started with Modin, you'll get Modin back (and compute will be distributed)
   • if you started with cuDF, you'll get cuDF back (and compute will happen on GPU)

What about Ibis?

Like Ibis, Narwhals aims to enable dataframe-agnostic code. However, Narwhals comes with zero dependencies, is about as lightweight as it gets, and is aimed at library developers rather than at end users. It also does not aim to support as many backends, instead preferring to focus on dataframes. So, which should you use?

• If you need to run complicated analyses and aren't too bothered about package size: Ibis!
• If you're a library maintainer and want the thinnest-possible layer to get cross-dataframe library support: Narwhals!

Here is the package size increase which would result from installing each tool in a non-pandas environment:

Example

See the tutorial for several examples!

Scope

• Do you maintain a dataframe-consuming library?
• Do you have a specific Polars function in mind that you would like Narwhals to have in order to make your work easier?

If you said yes to both, we'd love to hear from you!

Note: You might suspect that this is a secret ploy to infiltrate the Polars API everywhere. Indeed, you may suspect that.

Why "Narwhals"?

Coz they are so awesome.

Thanks to Olha Urdeichuk for the illustration!