pola-rs/polars

Add add_filename to pl.read_csv (and read operations others)

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#19,266 opened on Oct 16, 2024

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 (6 comments) (3 reactions) (0 assignees)Rust (38,496 stars) (2,826 forks)batch import
enhancementgood first issue

Description

Description

It is ocasionaly true that the filename of a data file is fairly critical information

Illustratively

Users/
   Alice.csv
   Bob.csv
   Charlie.csv

When using glob patterns to read this data, the file name itself is lost - which all but forces the user to loop over the files and read them manually.


# This does not preserve what row is for what user
df = pl.read_csv('Users/*.csv') 

 # This is a bit long
df = (pl.concat([
                pl.read_csv(file).with_columns(filename=pl.lit(file) 
                for file in glob('Users/*.csv')
            ])
        )

A parameter to add a column with the specific file name when reading data via a glob pattern would be a nice to have.

Contributor guide

Tech stack
pythonrust
Domain
data
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Polars Python APIRust FFI (pyo3)
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
The implementation involves adding a `add filename` parameter to `pl.read csv` (and other read functions like `read parquet`) in the Python API. This requires modifying the Python function signatures in `polars/py polars/polars/io/csv.py` and passing the parameter through to the Rust backend in `polars/polars io/src/csv.rs`. The column should contain the source filename or path. Review existing patterns like `include filepaths` or similar parameters in the codebase. Discussion in the issue comments may provide further context on desired behavior for multiple files vs single file.
Add add_filename to pl.read_csv (and read operations others) · pola-rs/polars#19266 | Good First Issue