Data Validation with Modin#

new in 0.8.0

Modin is a distributed compute framework that offers a pandas drop-in replacement dataframe implementation. You can use pandera to validate DataFrame() and Series() objects directly. First, install pandera with the dask extra:

pip install pandera[modin]       # installs both ray and dask backends
pip install pandera[modin-ray]   # only ray backend
pip install pandera[modin-dask]  # only dask backend

Then you can use pandera schemas to validate modin dataframes. In the example below we’ll use the class-based API to define a DataFrameModel for validation.

import modin.pandas as pd
import pandas as pd
import pandera as pa

from pandera.typing.modin import DataFrame, Series


class Schema(pa.DataFrameModel):
    state: Series[str]
    city: Series[str]
    price: Series[int] = pa.Field(in_range={"min_value": 5, "max_value": 20})


# create a modin dataframe that's validated on object initialization
df = DataFrame[Schema](
    {
        'state': ['FL','FL','FL','CA','CA','CA'],
        'city': [
            'Orlando',
            'Miami',
            'Tampa',
            'San Francisco',
            'Los Angeles',
            'San Diego',
        ],
        'price': [8, 12, 10, 16, 20, 18],
    }
)
print(df)
  state           city  price
0    FL        Orlando      8
1    FL          Miami     12
2    FL          Tampa     10
3    CA  San Francisco     16
4    CA    Los Angeles     20
5    CA      San Diego     18

You can also use the check_types() decorator to validate modin dataframes at runtime:

@pa.check_types
def function(df: DataFrame[Schema]) -> DataFrame[Schema]:
    return df[df["state"] == "CA"]

print(function(df))
  state           city  price
3    CA  San Francisco     16
4    CA    Los Angeles     20
5    CA      San Diego     18

And of course, you can use the object-based API to validate dask dataframes:

schema = pa.DataFrameSchema({
    "state": pa.Column(str),
    "city": pa.Column(str),
    "price": pa.Column(int, pa.Check.in_range(min_value=5, max_value=20))
})
print(schema(df))
  state           city  price
0    FL        Orlando      8
1    FL          Miami     12
2    FL          Tampa     10
3    CA  San Francisco     16
4    CA    Los Angeles     20
5    CA      San Diego     18