Extremely lightweight compatibility layer between pandas, Polars, cuDF, and Modin
Project description
Narwhals
Extremely lightweight compatibility layer between Polars, pandas, cuDF, and Modin.
Seamlessly support all four, without depending on any of them!
- ✅ 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 Polars Expressions
Note: this is work-in-progress, and a bit of an experiment, don't take it too seriously.
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:
-
use
narwhals.to_polars_apito wrap a pandas, Polars, cuDF, or Modin dataframe in the Polars API -
use the subset of the Polars API defined in https://github.com/MarcoGorelli/narwhals/blob/main/narwhals/spec/__init__.py.
-
use
DataFrame.to_nativeto return an object to the user in their 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
- if you started with cuDF, you'll get cuDF back (and computation will happen natively on the GPU!)
Example
Here's an example of a dataframe agnostic function:
from typing import TypeVar
import pandas as pd
import polars as pl
from narwhals import translate_frame
AnyDataFrame = TypeVar("AnyDataFrame")
def my_agnostic_function(
suppliers_native: AnyDataFrame,
parts_native: AnyDataFrame,
) -> AnyDataFrame:
suppliers, pl = translate_frame(suppliers_native)
parts, _ = translate_frame(parts_native)
result = (
suppliers.join(parts, left_on="city", right_on="city")
.filter(
pl.col("color").is_in(["Red", "Green"]),
pl.col("weight") > 14,
)
.group_by("s", "p")
.agg(
weight_mean=pl.col("weight").mean(),
weight_max=pl.col("weight").max(),
)
)
return result.to_native()
You can pass in a pandas, Polars, cuDF, or Modin dataframe, the output will be the same! Let's try it out:
suppliers = {
"s": ["S1", "S2", "S3", "S4", "S5"],
"sname": ["Smith", "Jones", "Blake", "Clark", "Adams"],
"status": [20, 10, 30, 20, 30],
"city": ["London", "Paris", "Paris", "London", "Athens"],
}
parts = {
"p": ["P1", "P2", "P3", "P4", "P5", "P6"],
"pname": ["Nut", "Bolt", "Screw", "Screw", "Cam", "Cog"],
"color": ["Red", "Green", "Blue", "Red", "Blue", "Red"],
"weight": [12.0, 17.0, 17.0, 14.0, 12.0, 19.0],
"city": ["London", "Paris", "Oslo", "London", "Paris", "London"],
}
print("pandas output:")
print(
my_agnostic_function(
pd.DataFrame(suppliers),
pd.DataFrame(parts),
)
)
print("\nPolars output:")
print(
my_agnostic_function(
pl.DataFrame(suppliers),
pl.DataFrame(parts),
)
)
print("\nPolars lazy output:")
print(
my_agnostic_function(
pl.LazyFrame(suppliers),
pl.LazyFrame(parts),
).collect()
)
pandas output:
s p weight_mean
0 S1 P6 19.0
1 S2 P2 17.0
2 S3 P2 17.0
3 S4 P6 19.0
Polars output:
shape: (4, 3)
┌─────┬─────┬─────────────┐
│ s ┆ p ┆ weight_mean │
│ --- ┆ --- ┆ --- │
│ str ┆ str ┆ f64 │
╞═════╪═════╪═════════════╡
│ S1 ┆ P6 ┆ 19.0 │
│ S3 ┆ P2 ┆ 17.0 │
│ S4 ┆ P6 ┆ 19.0 │
│ S2 ┆ P2 ┆ 17.0 │
└─────┴─────┴─────────────┘
Polars lazy output:
shape: (4, 3)
┌─────┬─────┬─────────────┐
│ s ┆ p ┆ weight_mean │
│ --- ┆ --- ┆ --- │
│ str ┆ str ┆ f64 │
╞═════╪═════╪═════════════╡
│ S1 ┆ P6 ┆ 19.0 │
│ S3 ┆ P2 ┆ 17.0 │
│ S4 ┆ P6 ┆ 19.0 │
│ S2 ┆ P2 ┆ 17.0 │
└─────┴─────┴─────────────┘
Magic! 🪄
Scope
- Do you maintain a dataframe-consuming library?
- Is there a Polars function which you'd like Narwhals to have, which would make your job easier?
If, I'd love to hear from you!
Note: this is not a "Dataframe Standard" project. It just translates a subset of the Polars API to pandas-like libraries.
Why "Narwhals"?
Because they are so awesome.
Release history Release notifications | RSS feed
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages.
Source Distribution
Built Distribution
File details
Details for the file narwhals-0.2.0.tar.gz.
File metadata
- Download URL: narwhals-0.2.0.tar.gz
- Upload date:
- Size: 130.5 kB
- Tags: Source
- Uploaded using Trusted Publishing? Yes
- Uploaded via: twine/4.0.2 CPython/3.11.8
File hashes
| Algorithm | Hash digest | |
|---|---|---|
| SHA256 | 22273a68b1857a10a5182aa2eaf750e8b15f58363b8280535cd1930b24cf3084 |
|
| MD5 | 561062b8dfa25e15f594dbbe6ebd05df |
|
| BLAKE2b-256 | 8355bee463b242c368ce8ca145e3886619abc0145415123ee452282f02793c41 |
File details
Details for the file narwhals-0.2.0-py3-none-any.whl.
File metadata
- Download URL: narwhals-0.2.0-py3-none-any.whl
- Upload date:
- Size: 24.2 kB
- Tags: Python 3
- Uploaded using Trusted Publishing? Yes
- Uploaded via: twine/4.0.2 CPython/3.11.8
File hashes
| Algorithm | Hash digest | |
|---|---|---|
| SHA256 | c2660db3af875fd16f27e72e72aee4b6f285124e2366c2f5e618fb5e29ca5112 |
|
| MD5 | db9c565d0a6cd6337ce577c98020162f |
|
| BLAKE2b-256 | f7c2480b98a20817de21a076add202b420382a2d18f0f218b1864b3cce3befd9 |
