What is Arnio?

Arnio is the data trust layer for Python. It answers one question:

"Is this data trustworthy?"

It answers through three verbs: validate, clean, and profile.

Think of it as Pydantic for DataFrames.

Install

pip install arnio

Quick Start

import arnio as ar
import pandas as pd

df = pd.DataFrame({
    "email": ["alice@example.com", "not-an-email", None],
    "age": [25, -5, 200],
    "name": ["Alice", "Bob", "Charlie"],
})

# Profile — instant data quality overview
report = ar.profile(df)
print(report.quality_score)  # 0–100

# Validate — check against a schema
schema = ar.Schema({
    "email": ar.Email(nullable=False),
    "age": ar.Int(min=0, max=150),
    "name": ar.String(min_length=1),
})
result = ar.validate(df, schema)
print(result.passed)   # False
print(result.issues)   # Structured list of issues

# Clean — declarative cleaning pipeline
cleaned = ar.clean(df, [
    "strip_whitespace",
    "drop_duplicates",
    ("normalize_case", {"case": "lower"}),
])

# Suggest — intelligent cleaning suggestions
suggestions = ar.suggest(df)

Three Core Verbs

Schema Definition

Two ways to define the same schema:

# Dict-based (dynamic, config-driven)
schema = ar.Schema({
    "email": ar.Email(nullable=False),
    "age": ar.Int(min=0, max=150),
    "name": ar.String(min_length=1),
})

# Class-based (IDE-friendly, inheritable)
class Customers(ar.Schema):
    email = ar.Email(nullable=False)
    age = ar.Int(min=0, max=150)
    name = ar.String(min_length=1)

Available Field Types

Cleaning Pipeline

# One-shot cleaning
cleaned = ar.clean(df, [
    "strip_whitespace",
    "drop_duplicates",
    ("fill_nulls", {"column": "category", "value": "unknown"}),
    "slugify_column_names",
])

# Reusable pipeline
pipe = ar.Pipeline([
    "strip_whitespace",
    "drop_duplicates",
    ("normalize_case", {"case": "lower"}),
])
cleaned = pipe.run(df)

# Save/load for version control
yaml_str = pipe.to_yaml()
pipe = ar.Pipeline.from_yaml(yaml_str)

Quality Gates (CI/CD)

# In a test file or CI script
ar.check(df, schema)  # Raises ar.ValidationError on failure

pandas Accessor

import arnio  # Registers the accessor

df.arnio.profile()
df.arnio.validate(schema)
df.arnio.clean(["strip_whitespace"])
df.arnio.suggest()
df.arnio.is_valid(schema)  # Returns bool

Works With

• pandas DataFrames (primary)
• dict / list of dicts (no pandas import needed for simple cases)
• Polars DataFrames (v2.1)

What Arnio Does NOT Do

Arnio stays in its lane. It does not:

• Query or filter data (use pandas/Polars)
• Perform analytics (use pandas/Polars/DuckDB)
• Do feature engineering (use scikit-learn)
• Create visualizations (use matplotlib/Plotly)
• Manage file formats (use PyArrow)

License

MIT — Anish Raj