Fast validation with error messages – `validate_data_fast`¶

Added in version 0.6.0: (experimental)

validate_data_fast is a preview of the next‑generation validation engine. It provides the the closest speed to compiled rules plus full error messages and support for nested dicts.

In a future release, validate_data_fast will become the default implementation of validate_data, keeping the exact same API but with dramatically better performance.

Use it today to speed up existing code with minimal changes.

Basic usage¶

from validatedata import validate_data_fast

result = validate_data_fast(
    data={'username': 'al', 'email': 'alice@example.com'},
    rule={
        'username': 'str|min:3|max:32',
        'email': 'email',
    },
)

if not result.ok:
    print(result.errors)   # ['username: string too short (minimum length: 3)']

# It returns the same `ValidationResult` as `validate_data`.

Differences from `validate_data`¶

Faster – uses compiled function calls, no per‑call recursion overhead.
No ``defaults`` parameter (yet) – but you can use mutate and raise_exceptions.
No ``keys`` wrapper – only bare dict rules (mirror‑structure) are supported.
No ``depends_on`` – conditional validation is not yet implemented in the fast path.
No custom transforms – only pipe‑syntax transforms (strip, lower, etc.) work.

All other features (pipe syntax, mirror‑structure, nullable, range, options, regex, custom error messages, and nested dicts) are fully supported.

Performance comparison¶

For a dict with 5 fields, validate_data_fast is typically 5–10x faster than validate_data and within 10% of the boolean‑only validator(), while still returning descriptive error messages.

# Instead of
result = validate_data(data, rule)

# Just change the function name
result = validate_data_fast(data, rule)

# Everything else stays the same

Current limitations (will be removed before merging)¶

No support for depends_on.
No support for custom callable transforms (only named pipe transforms).
No support for the {'keys': {...}} wrapper – use bare dicts.
No support for validating tuple/list of dicts with per‑position rules (but you can wrap the list in a dict or use a loop).

These limitations exist because the fast engine is still under development. They will be resolved before validate_data_fast replaces validate_data.

When to use¶

Existing projects – try replacing validate_data with validate_data_fast. If you don’t use the unsupported features, you get a free performance boost.
New projects – start with validate_data_fast and switch to validate_data only if you need depends_on or custom callable transforms.
High‑throughput APIs – use validator() for boolean checks, or validate_data_fast when you need error messages.

Feedback¶

This is an experimental feature. Please report any discrepancies between validate_data and validate_data_fast on the issue tracker – they help us ensure a smooth eventual merge.

Fast validation with error messages – validate_data_fast¶