Address Validator

FastAPI service (v2.0.0) that parses and standardizes US physical addresses per USPS Publication 28.

All API routes live under /api/v1/ and return an api_version field in every response body plus an API-Version: 1 response header.

Features

• Parse a raw address string into labelled components using the usaddress library.
• Standardize addresses to USPS format: all-caps, official suffix abbreviations (Avenue → AVE), directional abbreviations (South → S), state abbreviations (Illinois → IL), secondary unit designators (Suite → STE), and ZIP code normalization.
• Intersection support — "Hollywood Blvd and Vine St" → "HOLLYWOOD BLVD & VINE ST".
• Country validation — requests accept an optional country field (ISO 3166-1 alpha-2, default "US"). Invalid codes are rejected using the pycountry library; only US is currently supported.
• API key authentication — /api/v1/* endpoints require an X-API-Key header; docs remain open.
• CORS enabled — cross-origin requests are allowed from any origin.
• Health check — GET /api/v1/health for liveness probes.

Endpoints

Method	Path	Auth	Description
POST	/api/v1/parse	🔒	Parse raw address string into components
POST	/api/v1/standardize	🔒	Standardize address to USPS Pub 28 format
GET	/api/v1/health		Service health check
GET	/docs		Interactive Swagger UI
GET	/redoc		ReDoc API documentation

All POST endpoints accept and return application/json. Address inputs are limited to 1000 characters.

POST /api/v1/parse

Request:

{
  "address": "1600 Pennsylvania Avenue NW, Washington, DC 20500",
  "country": "US"
}

The country field is optional (defaults to "US").

Response:

{
  "input": "1600 Pennsylvania Avenue NW, Washington, DC 20500",
  "country": "US",
  "components": {
    "spec": "usps-pub28",
    "spec_version": "unknown",
    "values": {
      "address_number": "1600",
      "street_name": "Pennsylvania",
      "street_name_post_type": "Avenue",
      "street_name_post_directional": "NW",
      "city": "Washington",
      "state": "DC",
      "zip_code": "20500"
    }
  },
  "type": "Street Address",
  "warnings": [],
  "api_version": "1"
}

The type field is one of "Street Address", "Intersection", or "Ambiguous". The warnings list is populated whenever input is silently modified during parsing — for example when parenthesized text is stripped, when repeated address numbers are joined into a range, or when a unit designator is recovered from a mis-tagged field. It is empty on clean input.

The components field is a ComponentSet containing:

• spec — machine identifier for the component schema (e.g. "usps-pub28").
• spec_version — edition of the spec the values conform to.
• values — the labelled address component key/value pairs.

POST /api/v1/standardize

Accepts either a raw address string or pre-parsed components. When both are provided, components takes precedence and address is ignored.

Request (string):

{
  "address": "350 Fifth Ave Suite 3300, New York, NY 10118",
  "country": "US"
}

Request (components):

{
  "components": {
    "address_number": "350",
    "street_name": "Fifth",
    "street_name_post_type": "Ave",
    "occupancy_type": "Suite",
    "occupancy_identifier": "3300",
    "city": "New York",
    "state": "NY",
    "zip_code": "10118"
  },
  "country": "US"
}

Response:

{
  "address_line_1": "350 FIFTH AVE",
  "address_line_2": "STE 3300",
  "city": "NEW YORK",
  "region": "NY",
  "postal_code": "10118",
  "country": "US",
  "standardized": "350 FIFTH AVE  STE 3300  NEW YORK, NY 10118",
  "components": {
    "spec": "usps-pub28",
    "spec_version": "unknown",
    "values": {
      "address_number": "350",
      "street_name": "FIFTH",
      "street_name_post_type": "AVE",
      "occupancy_type": "STE",
      "occupancy_identifier": "3300",
      "city": "NEW YORK",
      "state": "NY",
      "zip_code": "10118"
    }
  },
  "warnings": [],
  "api_version": "1"
}

The response uses geography-neutral field names: region (not state) and postal_code (not zip_code). The standardized field uses two-space separators between address lines, matching the USPS single-line format convention.

GET /api/v1/health

Response:

{"status": "ok", "api_version": "1"}

No authentication required.

Authentication

All /api/v1/* endpoints (except /api/v1/health) require an X-API-Key header. Set the expected key via the API_KEY environment variable:

export API_KEY=$(python3 -c 'import secrets; print(secrets.token_urlsafe(32))')

Requests without a valid key receive 401 or 403. Swagger (/docs) and ReDoc (/redoc) remain open.

curl -X POST http://localhost:8000/api/v1/standardize \
  -H 'Content-Type: application/json' \
  -H 'X-API-Key: YOUR_KEY' \
  -d '{"address": "350 Fifth Ave, New York, NY 10118"}'

Setup

Requires Python ≥ 3.12. Dependencies are managed with uv.

uv sync                  # install dependencies into .venv/
export API_KEY="your-secret-key"
uv run uvicorn main:app --host 0.0.0.0 --port 8000

A systemd unit file (address-validator.service) is included for persistent deployment. The API key is stored in /etc/address-validator/env and loaded via EnvironmentFile=.

Project Structure

main.py                        # FastAPI app entry point, CORS config
auth.py                        # API key authentication dependency
models.py                      # Shared Pydantic request/response models
routers/
  v1/
    core.py                    # Country validation, APIError, helpers
    health.py                  # GET /api/v1/health
    parse.py                   # POST /api/v1/parse
    standardize.py             # POST /api/v1/standardize
services/
  parser.py                    # usaddress wrapper, tag-name mapping
  standardizer.py              # USPS Pub 28 standardization logic
usps_data/
  spec.py                      # Pub 28 spec identifier constants
  suffixes.py                  # Street suffix abbreviations
  directionals.py              # Directional abbreviations
  states.py                    # State name → abbreviation map
  units.py                     # Secondary unit designators
docs/
  usps-pub28.md                # Pub 28 research notes
  usps-addresses-v3r2_3.yaml   # Archived USPS Addresses API v3 spec
tests/
  conftest.py                  # Shared fixtures, API_KEY bootstrap
  unit/                        # Unit tests (parser, standardizer, auth, data)
  integration/                 # Integration tests (HTTP endpoints)
address-validator.service      # systemd unit file
pyproject.toml                 # Project metadata, dependencies, tool config

Standardization Rules Applied

• All output uppercased
• Parenthesized text removed (USPS Pub 28 §354 — not valid in standardized addresses; typically wayfinding notes)
• Trailing commas, semicolons, and stray punctuation stripped
• Street suffixes abbreviated (USPS Pub 28 Appendix C)
• Directionals abbreviated (N, S, E, W, NE, NW, SE, SW)
• State names converted to two-letter abbreviations
• Secondary unit designators abbreviated (Suite → STE, Apartment → APT, Building/Bldg/Bld → BLDG, etc.)
• Unit identifiers without a designator default to #
• Designator words folded into identifiers are extracted (e.g. NO. 16 → # 16)
• Both occupancy and subaddress designators preserved when present
• Dual address numbers joined with hyphen (1804 & 1810 → 1804-1810)
• Periods removed from all components
• ZIP codes normalized to 5-digit or 5+4 format
• Unit designators mis-tagged as city by the parser are recovered (e.g. BASEMENT, FREELAND → line 2 BSMT, city FREELAND)
• Non-address wayfinding words (e.g. YARD) dropped from city
• Line 2 ordering: larger container (BLDG) before specific unit (STE)
• Intersections formatted as STREET1 & STREET2

Testing

uv run pytest                          # full suite with coverage
uv run pytest --no-cov                 # fast, no coverage
uv run pytest tests/unit/test_parser.py # single file
uv run ruff check .                    # lint
uv run ruff format .                   # format

Coverage floor: 80% line + branch (enforced by --cov-fail-under=80).