Export

The export module writes datasets to various file formats. It supports CSV, JSON, Parquet, Arrow, and DataFrame interchange.

Dataset Methods

The primary way to export data is through the Dataset object:


import hermes as hr
 
ds = hr.Dataset(name="gdp", data_ref="gdp.csv", data=df)
 
# Save to disk (writes to directory)
ds.save("output/", format="parquet")   # -> output/gdp.parquet
ds.save("output/", format="csv")       # -> output/gdp.csv
ds.save("output/", format="json")      # -> output/gdp.json
 
# Export to raw bytes
csv_bytes = ds.export("csv")
parquet_bytes = ds.export("parquet")
json_bytes = ds.export("json")
 
# Export as dataframes
polars_df = ds.export("polars")        # -> pl.DataFrame
arrow_tbl = ds.export("arrow")        # -> pa.Table
pandas_df = ds.export("pandas")       # -> pd.DataFrame

export() Utility

Low-level export function:


from hermes.export import export
import polars as pl
 
df = pl.read_csv("data.csv")
 
# Export to CSV
export(data=df, filetype="csv", loc="output/", name="my_data")
 
# Export to JSON
export(data=df, filetype="json", loc="output/", name="my_data")
 
# Export to Parquet
export(data=df, filetype="parquet", loc="output/", name="my_data")

Parameters

Parameter	Type	Default	Description
`data`	`pl.DataFrame`	(required)	Data to export
`filetype`	`str`	`"csv"`	Output format: `csv`, `json`, `parquet`
`loc`	`Path \| str`	`"data/"`	Output directory
`name`	`str \| None`	`None`	Filename (without extension). If `None`, uses timestamp

The function creates the target directory if it doesn’t exist.

Format Support

Format	File Extension	Method
CSV	`.csv`	`pl.DataFrame.write_csv()`
JSON	`.json`	`pl.DataFrame.write_json()`
Parquet	`.parquet`	`pl.DataFrame.write_parquet()`

Interchange Formats

Convert to other DataFrame libraries:


import hermes as hr
 
ds = hr.Dataset(name="gdp", data=df)
 
# Polars
polars_df = ds.to_polars()   # -> pl.DataFrame
 
# PyArrow
arrow_tbl = ds.to_arrow()    # -> pa.Table
 
# Pandas
pandas_df = ds.to_pandas()   # -> pd.DataFrame

Top-Level API


import hermes as hr
 
result = hr.save(data, path="output/", format="parquet")