Polars dfs is 0-based indexed if no conversion to data.frame explicitly

[ivan-balashov]

Hi! I've found that while Polars dataframes can be used, the indices cannot be properly used without explicit conversion to a data frame (still 0-based indexing instead of the 1-based indexing used in Pandas conversion). I think there should be some kind of warning about this at least.

Test pandas and polars dfs

import pandas as pd
import polars as pl

data = {'aa':[1,2,3,4,5,6,7,8,9,10,11,12]}

pl_df  = pl.DataFrame(data)
pd_df  = pd.DataFrame(data)

library(reticulate)
head(py$pd_df)

  aa
1  1
2  2
3  3
4  4
5  5
6  6

head(as.data.frame(py$pd_df))

  aa
1  1
2  2
3  3
4  4
5  5
6  6

head(py$pl_df)

shape: (6, 1)
┌─────┐
│ aa  │
│ --- │
│ i64 │
╞═════╡
│ 2   │
│ 3   │
│ 4   │
│ 5   │
│ 6   │
│ 7   │
└─────┘

head(as.data.frame(py$pl_df))

  aa
1  1
2  2
3  3
4  4
5  5
6  6

utils::sessionInfo() 

R version 4.4.2 (2024-10-31)
Platform: x86_64-apple-darwin20
Running under: macOS Ventura 13.5.1

Matrix products: default
BLAS:   /Library/Frameworks/R.framework/Versions/4.4-x86_64/Resources/lib/libRblas.0.dylib 
LAPACK: /Library/Frameworks/R.framework/Versions/4.4-x86_64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.0

locale:
[1] ru_RU.UTF-8/ru_RU.UTF-8/ru_RU.UTF-8/C/ru_RU.UTF-8/ru_RU.UTF-8

time zone: 
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base     

other attached packages:
[1] reticulate_1.40.0

loaded via a namespace (and not attached):
 [1] digest_0.6.37     fastmap_1.2.0     xfun_0.49         Matrix_1.7-1     
 [5] lattice_0.22-6    knitr_1.49        htmltools_0.5.8.1 png_0.1-8        
 [9] rmarkdown_2.29    cli_3.6.3         grid_4.4.2        renv_1.0.11      
[13] compiler_4.4.2    tools_4.4.2       evaluate_1.0.1    Rcpp_1.0.13-1    
[17] yaml_2.3.10       rlang_1.1.4       jsonlite_1.8.9   

reticulate::py_config()

python:        my_folder/.venv/bin/python
libpython:      /Users/ivanbalashov/.local/share/uv/python/cpython-3.12.7-macos-x86_64-none/lib/libpython3.12.dylib
pythonhome:     my_folder/.venv
virtualenv:     my_folder/.venv/bin/activate_this.py
version:        3.12.7 (main, Oct 16 2024, 09:10:10) [Clang 18.1.8 ]
numpy:         my_folder/.venv/lib/python3.12/site-packages/numpy
numpy_version:  2.2.0

NOTE: Python version was forced by VIRTUAL_ENV