v6e 0.1.4

A simple, type-safe, and extensible Python validations framework

🔍 V6E

A simple, type-safe, and extensible Python validations framework

Why the name?

v6e comes from the numeronym of "validate".

Examples

Check out the examples in ./examples! You can run them locally with:

uv run examples/validations.py

Usage

Basic validations

import v6e as v

my_validation = v.int().gte(18).lte(21)

# Use it only to check if the value conforms
my_validation.check(18)  # True
my_validation.check(21)  # True
my_validation.check(54)  # False

# Use `.parse()` to validate and get the parsed value
my_validation.parse(21)  # Ok -> Returns 21 (int)
my_validation.parse("21")  # Ok -> Returns 21 (int)
my_validation.parse(54)  # Err -> Raises a ValidationException

Chaining your validations and transformations

my_validation = v.str().trim().starts_with("foo").ends_with("foo").regex(r"^[a-z0-9]*$")
my_validation.parse("  foo12")  # Ok -> Returns 'foo12' (str)
my_validation.parse("12foo  ")  # Ok -> Returns '12foo' (str)
my_validation.parse("1foo2")  # Err -> Raises a ValidationException

Handling multiple possible types

union = v.str().starts_with("foo") | v.int().gte(5)

union.parse("foobar")  # Ok -> Returns 'foobar' (str)
union.parse("1foo2")  # Err -> Raises a ValidationException

union.parse(5)  # Ok -> Returns 5 (int)
union.parse(3)  # Err -> Raises a ValidationException

union.parse(None)  # Err -> Raises a ValidationException

Custom validations

def _validate_earth_age(x: int) -> None:
    if x != 4_543_000_000:
        raise ValueError("The Earth is 4.543 billion years old. Try 4543000000.")

earth_age = v.int().custom(_validate_earth_age)
earth_age.parse(4_543_000_000)  # Ok -> Returns 4_543_000_000 (int)
earth_age.parse("4543000000")  # Ok -> Returns 4_543_000_000 (int)
earth_age.parse(1)  # Err -> Raises ValidationException

Custom reusable types

class DivThree(v.IntType):
    @override
    def parse_raw(self, raw: t.Any):
        parsed: int = super().parse_raw(raw)
        if parsed % 3 != 0:
            raise ValueError(f"Woops! {parsed!r} is not divisible by three")


my_validation = DivThree().gt(5)
my_validation.parse(6)  # Ok -> Returns 6
my_validation.parse(3)  # Err (not >5) -> Raises a ValidationException
my_validation.parse(7)  # Err (not div by 3) -> Raises a ValidationException

🐍 Type-checking

This library is fully type-checked. This means that all types will be correctly inferred from the arguments you pass in.

In this example your editor will correctly infer the type:

my_validation = v.int().gte(8).lte(4)
t.reveal_type(my_validation)  # Type of "my_validation" is "V6eInt"
t.reveal_type(my_validation.check)  # Type of "my_validation.check" is "(raw: Any) -> bool"
t.reveal_type(my_validation.safe_parse)  # Type of "my_validation" is "(raw: Any) -> V6eResult[int]"
t.reveal_type(my_validation.parse)  # Type of "my_validation" is "(raw: Any) -> int"

Why do I care?

Type checking will help you catch issues way earlier in the development cycle. It will also provide nice autocomplete features in your editor that will make you faster ⚡.