Pandera MWE – I want a single failure case when region_is_valid fails indicating the sample_name of the row that failed (cDNA-VOC-1-v4-1)

custom_check.py

from io import StringIO

import pandas as pd
import pandera as pa
import pandera.extensions as extensions
from pandera.typing import Index, Series

csv_string = """
sample_name,country,region
cDNA-VOC-1-v4-1,USA,Bretagne
cDNA-VOC-1-v4-2,USA,Texas
"""

# Bretagne is not in the USA, so should fail the check

countries_subdivisions = {'USA': ['Texas'], 'France': ['Bretagne']}
COUNTRIES_ALPHA_3 = set(countries_subdivisions.keys())
REGIONS = {i for l in countries_subdivisions.values() for i in l}


@extensions.register_check_method()
def region_is_valid(df):
    """
    Validate the region field using ISO-3166
    """

    def validate_region(row):
        if not pd.isna(row["region"]) and row["region"] not in countries_subdivisions.get(
            row["country"]
        ):
            valid = False
        else:
            valid = True
        return valid

    return df.apply(validate_region, axis=1)


# @extensions.register_check_method()
# def is_texas(df):
#     return df['region'] == 'Texas'


class BaseSchema(pa.SchemaModel):
    """
    Validate generic GPAS upload CSVs
    """

    sample_name: Index[str] = pa.Field(str_matches=r"^[A-Za-z0-9._-]+$", unique=True, coerce=True, nullable=False)
    country: Series[str] = pa.Field(isin=COUNTRIES_ALPHA_3, coerce=True, nullable=False)
    region: Series[str] = pa.Field(nullable=True, isin=REGIONS, coerce=True)

    class Config:
        region_is_valid = ()
        # is_texas = ()


def main():
    df = pd.read_csv(StringIO(csv_string), index_col=0)
    try:
        BaseSchema.validate(df, lazy=True)
    except pa.errors.SchemaErrors as e:
        print(e.failure_cases)


if __name__ == '__main__':
    main()

This script outputs the following:

% python mwe.py
    schema_context   column            check  check_number failure_case            index
0  DataFrameSchema  country  region_is_valid             0          USA  cDNA-VOC-1-v4-1
1  DataFrameSchema   region  region_is_valid             0     Bretagne  cDNA-VOC-1-v4-1

I'd like to have a single failure case per failing row – is this possible?

Clearly I could do e.failure_cases.groupby('index')['check'].unique(), but perhaps there is a Right Way to do this : ) @cosmicBboy