Does Polars module not have a method for appending DataFrames to output files?

Question

Sorry for the question but I’m starting out with polars library.

I was reading the documentation for Polars DataFrame and found that any of the .write_* methods have the argument mode.
While pandas DataFrame has the .to_csv() method with the mode parameter available, thus allowing to append the DataFrame to a file.
None of the Polars DataFrame output methods seems to have that parameter.

Am I missing something?
How should I Append a Polar DataFrame to a file using polars?
Should I instead include csv or pandas modules into my code?

Asked By: Mr. Caribbean

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Source

Answer 1

To append to a CSV file for example – you can pass a file object e.g.

import polars as pl

df1 = pl.DataFrame({"a": [1, 2], "b": [3 ,4]})
df2 = pl.DataFrame({"a": [5, 6], "b": [7 ,8]})

with open("out.csv", mode="ab") as f:
   df1.write_csv(f)
   df2.write_csv(f, has_header=False)

>>> from pathlib import Path
>>> print(Path("out.csv").read_text(), end="")
a,b
1,3
2,4
5,7
6,8

Answered By: jqurious

Does Polars module not have a method for appending DataFrames to output files?

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