typewall 0.0.1

Runtime type validation for Python

TypeWall

Runtime type validation for Python with a small, schema-first API.

from typewall import w

User = w.object({
    "name": w.str(),
    "age": w.int().optional(),
    "tags": w.list(w.str()).default([]),
})

user = User.parse({"name": "Ada"})
assert user == {"name": "Ada", "tags": []}

Use safe_parse() when validation failures should be returned instead of raised:

result = User.safe_parse({"name": 42})

if not result.ok:
    print(result.to_dict())

The MVP supports strict string, integer, float, boolean, object, and list schemas; required, optional, and defaulted fields; and structured validation errors. It does not coerce values. Constraints, advanced composition, transforms, type-derived schemas, schema export, environment parsing, CLI tools, and framework integrations are intentionally deferred to later phases.

MVP Public API

• Builders: w, tw, and SchemaBuilder
• Schemas: Schema, StringSchema, IntegerSchema, FloatSchema, BooleanSchema, ObjectSchema, and ListSchema
• Parsing: Schema.parse() and Schema.safe_parse()
• Field configuration: Schema.optional() and Schema.default()
• Results and errors: ParseResult, ValidationIssue, and ValidationError

MVP object schemas reject unknown keys, omit absent optional fields, defensively copy defaults, and aggregate independently reachable issues in deterministic order. The error dictionary uses $ for root failures and dot-delimited paths for nested fields and list indexes.

Development

TypeWall uses uv and supports CPython 3.9 through 3.14.

UV_CACHE_DIR=.uv-cache uv sync --python 3.14
UV_CACHE_DIR=.uv-cache uv run pytest
UV_CACHE_DIR=.uv-cache uv run ruff check .
UV_CACHE_DIR=.uv-cache uv run mypy