usps-v3 1.0.1

Python SDK for USPS Web Tools v3 REST API — OAuth 2.0, address validation, tracking, labels, prices

usps-v3

Python SDK for the USPS Web Tools v3 REST API — the replacement for the retired XML-based Web Tools.

Direct USPS integration. OAuth 2.0. No middleman. No per-label fees.

Install

pip install usps-v3

Quick Start

from usps_v3 import Client

# Credentials from USPS Business Customer Gateway
client = Client(client_id="your-id", client_secret="your-secret")
# Or set USPS_CLIENT_ID and USPS_CLIENT_SECRET environment variables:
# client = Client()

# Validate an address (FREE)
result = client.addresses.validate(
    street_address="1600 Pennsylvania Ave NW",
    city="Washington",
    state="DC",
    zip_code="20500",
)
print(result["address"]["ZIPPlus4"])  # "0005"

# Track a package (FREE)
info = client.tracking.track("9400111899223033005282")
print(info["statusCategory"])  # "Delivered"

# Get delivery time estimates (FREE)
standards = client.standards.estimates("10001", "90210")

# Find drop-off locations (FREE)
locations = client.locations.dropoff("20500", mail_class="PRIORITY_MAIL")

# Get rate quotes
rates = client.prices.domestic("10001", "90210", weight=2.5)
print(rates["rates"]["rateOptions"][0]["totalPrice"])

# International rates
intl = client.prices.international("10001", "CA", weight=3.0)

# Create shipping labels (requires USPS enrollment + COP claims)
label = client.labels.create(
    from_address={"streetAddress": "123 Sender St", "city": "New York", "state": "NY", "ZIPCode": "10001"},
    to_address={"streetAddress": "456 Recipient Ave", "city": "LA", "state": "CA", "ZIPCode": "90001"},
    mail_class="PRIORITY_MAIL",
    weight=2.0,
)
print(label["trackingNumber"])

# Void a label
client.labels.void("9400111899223033005282")

Features

Feature	Endpoint	Auth Required
Address Validation	addresses.validate()	OAuth only
City/State Lookup	addresses.city_state()	OAuth only
Package Tracking	tracking.track()	OAuth only
Service Standards	standards.estimates()	OAuth only
Drop-off Locations	locations.dropoff()	OAuth only
Domestic Prices	prices.domestic()	OAuth only
International Prices	prices.international()	OAuth only
Label Creation	labels.create()	OAuth + Payment Auth
Label Void	labels.void()	OAuth only

Authentication

The SDK handles OAuth 2.0 token lifecycle automatically:

• Token caching: Tokens are cached in memory and on disk (~/.usps-v3/tokens.json)
• Auto-refresh: Tokens refresh automatically 30 minutes before expiry
• Thread-safe: Safe for concurrent use across threads

Getting Credentials

1. Register at USPS Business Customer Gateway
2. Create an application in the API developer portal
3. Note your client_id and client_secret

For label creation, you also need:

• CRID (Customer Registration ID)
• MIDs (Mailer IDs — master + label owner)
• EPA (Enterprise Payment Account)
• COP claims linking at cop.usps.com

client = Client(
    client_id="...",
    client_secret="...",
    crid="56982563",
    master_mid="904128936",
    label_mid="904128937",
    epa_account="1000405525",
)

Error Handling

from usps_v3 import Client, AuthError, ValidationError, RateLimitError, APIError

try:
    result = client.addresses.validate(street_address="123 Main St")
except ValidationError as e:
    print(f"Bad input: {e} (field: {e.field})")
except RateLimitError as e:
    print(f"Rate limited — retry after {e.retry_after}s")
except AuthError as e:
    print(f"Auth failed: {e}")
except APIError as e:
    print(f"USPS error ({e.status_code}): {e}")

USPS Rate Limits

The v3 API defaults to 60 requests/hour (down from unlimited in Web Tools). The SDK does not enforce this limit — USPS returns 429 when exceeded.

To request a higher limit, contact USPS at emailus.usps.com.

Migration from Web Tools

If you're migrating from the retired USPS Web Tools XML API:

Web Tools (XML)	v3 SDK (Python)
<AddressValidateRequest>	client.addresses.validate(...)
<CityStateLookupRequest>	client.addresses.city_state(...)
<TrackFieldRequest>	client.tracking.track(...)
<RateV4Request>	client.prices.domestic(...)
User ID auth	OAuth 2.0 (automatic)
XML response parsing	Python dicts (automatic)
Unlimited requests	60/hr default (request increase)

Development

git clone https://github.com/revereveal/usps-v3.git
cd usps-v3
pip install -e ".[dev]"
pytest -v

License

MIT — see LICENSE.

Built by RevAddress — direct USPS API integration for developers.