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Cannot load the dataset split (in streaming mode) to extract the first rows.
Error code:   StreamingRowsError
Exception:    CastError
Message:      Couldn't cast
iso_639_3: string
script: string
language_code: string
language_name: string
character: string
unicode_category: string
unicode_name: string
total_frequency_all_time: int64
time_periods_with_data_count: int64
time_periods_list: string
year_2013_frequency: int64
year_2014_frequency: int64
year_2016_frequency: int64
year_2017_frequency: int64
year_2018_frequency: int64
year_2019_frequency: int64
year_2020_frequency: int64
year_2023_frequency: int64
-- schema metadata --
pandas: '{"index_columns": [{"kind": "range", "name": null, "start": 0, "' + 2628
to
{'iso_639_3': Value('string'), 'script': Value('string'), 'language_code': Value('string'), 'language_name': Value('string'), 'character': Value('string'), 'unicode_category': Value('string'), 'unicode_name': Value('string'), 'total_frequency_all_time': Value('int64'), 'time_periods_with_data_count': Value('int64'), 'time_periods_list': Value('string'), 'year_2016_frequency': Value('int64'), 'year_2017_frequency': Value('int64'), 'year_2018_frequency': Value('int64'), 'year_2019_frequency': Value('int64'), 'year_2020_frequency': Value('int64')}
because column names don't match
Traceback:    Traceback (most recent call last):
                File "/src/services/worker/src/worker/utils.py", line 99, in get_rows_or_raise
                  return get_rows(
                         ^^^^^^^^^
                File "/src/libs/libcommon/src/libcommon/utils.py", line 272, in decorator
                  return func(*args, **kwargs)
                         ^^^^^^^^^^^^^^^^^^^^^
                File "/src/services/worker/src/worker/utils.py", line 77, in get_rows
                  rows_plus_one = list(itertools.islice(ds, rows_max_number + 1))
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/iterable_dataset.py", line 2431, in __iter__
                  for key, example in ex_iterable:
                                      ^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/iterable_dataset.py", line 1952, in __iter__
                  for key, pa_table in self._iter_arrow():
                                       ^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/iterable_dataset.py", line 1975, in _iter_arrow
                  for key, pa_table in self.ex_iterable._iter_arrow():
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/iterable_dataset.py", line 503, in _iter_arrow
                  for key, pa_table in iterator:
                                       ^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/iterable_dataset.py", line 350, in _iter_arrow
                  for key, pa_table in self.generate_tables_fn(**gen_kwags):
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/packaged_modules/parquet/parquet.py", line 106, in _generate_tables
                  yield f"{file_idx}_{batch_idx}", self._cast_table(pa_table)
                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/packaged_modules/parquet/parquet.py", line 73, in _cast_table
                  pa_table = table_cast(pa_table, self.info.features.arrow_schema)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/table.py", line 2272, in table_cast
                  return cast_table_to_schema(table, schema)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.12/site-packages/datasets/table.py", line 2218, in cast_table_to_schema
                  raise CastError(
              datasets.table.CastError: Couldn't cast
              iso_639_3: string
              script: string
              language_code: string
              language_name: string
              character: string
              unicode_category: string
              unicode_name: string
              total_frequency_all_time: int64
              time_periods_with_data_count: int64
              time_periods_list: string
              year_2013_frequency: int64
              year_2014_frequency: int64
              year_2016_frequency: int64
              year_2017_frequency: int64
              year_2018_frequency: int64
              year_2019_frequency: int64
              year_2020_frequency: int64
              year_2023_frequency: int64
              -- schema metadata --
              pandas: '{"index_columns": [{"kind": "range", "name": null, "start": 0, "' + 2628
              to
              {'iso_639_3': Value('string'), 'script': Value('string'), 'language_code': Value('string'), 'language_name': Value('string'), 'character': Value('string'), 'unicode_category': Value('string'), 'unicode_name': Value('string'), 'total_frequency_all_time': Value('int64'), 'time_periods_with_data_count': Value('int64'), 'time_periods_list': Value('string'), 'year_2016_frequency': Value('int64'), 'year_2017_frequency': Value('int64'), 'year_2018_frequency': Value('int64'), 'year_2019_frequency': Value('int64'), 'year_2020_frequency': Value('int64')}
              because column names don't match

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FineFreq is a large-scale multilingual character frequency dataset derived from 96.6 trillion characters across 1900+ languages, built from the FineWeb and FineWeb2 corpora. It provides per-language frequency tables with year-level temporal resolution, covering the period 2013–2025.


Dataset Structure

Each file (per language-script pair) contains fields as follows:

Column Description
iso_639_3 ISO 639‑3 language code
script Unicode script (e.g. Latn, Cyrl, Hani)
language_code Combined language-script tag (e.g. eng_Latn)
language_name Human-readable language name
character Unicode character
unicode_category Unicode general category (e.g. Ll, Lo, Pd)
unicode_name Official Unicode character name
total_frequency_all_time Total count of the character across all available years
time_periods_with_data_count Number of years with observed data
time_periods_list List of years in which the character appeared
year_20XX_frequency Character frequency per year (e.g. year_2017_frequency)

Not all languages have full year coverage. Frequencies are raw counts (not percentages), normalized later as needed.

Two manifest files are included for quick indexing:

  • manifest/languages.csv
  • manifest/languages.parquet

Each row contains metadata per language-script pair:

Field Description
iso_639_3 ISO 639‑3 code
language_code Language-script ID
script Script used
language_name Full language name
total_frequency Sum of all character frequencies
data_source FineWeb or FineWeb2
years_count Number of years with data
min_year, max_year First and last year of data coverage

Usage

Load a single language dataset (e.g. English)

Use the standard Hugging Face load_dataset function to load data for any language.

from datasets import load_dataset

# Load character frequency data for English (eng_Latn)
ds = load_dataset(
    "lgi2p/finefreq",
    data_files="DATA/eng_Latn/eng_Latn.parquet",  # Use .csv for CSV format
    split="train"
)

# Convert to pandas DataFrame for analysis
df = ds.to_pandas()

# Display the top 20 characters by total frequency
df_sorted = df.sort_values("total_frequency_all_time", ascending=False)
print(df_sorted[["character", "unicode_name", "total_frequency_all_time"]].head(20))

Browse available languages

Before loading data, you can check which languages are available in the dataset.

import pandas as pd
from huggingface_hub import hf_hub_download

# Download and read the manifest file
manifest_path = hf_hub_download(
    repo_id="lgi2p/finefreq",
    filename="manifest/languages.csv",
    repo_type="dataset"
)
manifest_df = pd.read_csv(manifest_path)

# Show a summary of available languages
print(f"Total languages available: {len(manifest_df)}")
print("\nLanguages with the most character occurrences:")
print(manifest_df.nlargest(10, 'total_frequency')[['language_code', 'script', 'total_frequency']])

Optional: Helper function to load any language by code

def load_finefreq(language_code: str, format="parquet"):
    """
    Load a FineFreq language dataset.
    
    Args:
        language_code: Language identifier (e.g., 'eng_Latn', 'fra_Latn')
        format: File format ('parquet' or 'csv')
    
    Returns:
        pandas.DataFrame with character frequency data
    """
    from datasets import load_dataset
    ext = "csv" if format == "csv" else "parquet"
    ds = load_dataset(
        "lgi2p/finefreq",
        data_files=f"DATA/{language_code}/{language_code}.{ext}",
        split="train"
    )
    return ds.to_pandas()

# Example usage
df_english = load_finefreq("eng_Latn")
df_french = load_finefreq("fra_Latn")

Notes

  • Replace "eng_Latn" with any language code listed in manifest/languages.csv.
  • Both .parquet and .csv files are available for each language.
  • Parquet is recommended for faster loading; CSV is human-readable and previewable on the Hugging Face Hub.
  • Each language folder also contains a metadata.json file with summary statistics and source information.

Citation

@article{Xu2025finefreq,
  title={FineFreq: A Multilingual Character Frequency Dataset from Web-Scale Text},
  author={Binbin Xu},
  journal={arXiv preprint arXiv:2512.09701},
  year={2025}, 
  url = {https://arxiv.org/abs/2512.09701}
}
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