postpin

Official Python SDK for the Postpin shipping-rate API — calculate courier charges between Indian pincodes, check serviceability, look up the pincode directory, and verify webhooks.

• Fully typed — dataclass results and typed parameters; ships py.typed.
• Robust by default — automatic retries with exponential backoff + jitter, Retry-After support, per-request timeouts, and idempotency keys.
• Typed errors — catch RateLimitError, QuotaExceededError, ValidationError, and friends.
• Secure webhooks — constant-time HMAC signature verification with replay protection.

Requirements

• Python 3.8+

Install

pip install postpin

Quick start

import os
from postpin import Postpin

client = Postpin(os.environ["POSTPIN_API_KEY"])

rate = client.rates.calculate(
    origin="400001",       # Mumbai
    destination="110001",  # New Delhi
    weight=1200,           # grams
    service="express",     # "surface" | "express" | "same_day"
)

print(rate.total, rate.currency)  # 254.38 INR
print(rate.eta_days)              # [1, 3]
for line in rate.breakdown:
    print(line.label, line.amount)

Load your API key from an environment variable — never hard-code it.

The client can be used as a context manager to close the connection pool:

with Postpin(api_key) as client:
    rate = client.rates.calculate(origin="400001", destination="781001", weight=2500)

Configuration

client = Postpin(
    api_key,
    base_url="https://api.postpin.in/v1",  # override the API base (incl. version)
    timeout=30.0,                          # per-request timeout in seconds
    max_retries=2,                         # retries on 429/5xx/network errors
    headers={"x-team": "logistics"},       # extra headers on every request
)

Resources

# Rates
rate = client.rates.calculate(
    origin="400001", destination="781001", weight=2500,
    length=30, width=20, height=15,   # cm — enables volumetric weight
    cod=True, declared_value=4999,    # rupees
)

# Serviceability
check = client.serviceability.check("781001")
print(check.serviceable, check.city)

# Pincodes
pin = client.pincodes.get("302001")
states = client.pincodes.states()

# Plans
plans = client.plans.list()

Every method accepts timeout=, and rates.calculate also accepts idempotency_key=.

Error handling

from postpin import (
    Postpin, RateLimitError, QuotaExceededError,
    ValidationError, AuthenticationError, NotFoundError,
)

try:
    client.rates.calculate(origin="400001", destination="110001", weight=1200)
except RateLimitError as e:
    print(f"Rate limited — retry after {e.retry_after}s")
except QuotaExceededError:
    print("Monthly quota exhausted — upgrade your plan")
except ValidationError as e:
    print("Bad request:", e.message, e.details)
except AuthenticationError:
    print("Invalid API key")

Every PostpinError carries code, status_code, request_id, details, and headers.

Webhooks

Verify against the raw request body — re-serializing the JSON breaks the signature.

from flask import Flask, request
from postpin import webhooks, SignatureVerificationError

app = Flask(__name__)

@app.post("/webhooks/postpin")
def handle():
    try:
        event = webhooks.construct_event(
            request.get_data(),                       # raw bytes
            request.headers.get("X-Postpin-Signature"),
            os.environ["POSTPIN_WEBHOOK_SECRET"],
        )
    except SignatureVerificationError:
        return "", 400

    if event["event"] == "rate.calculated":
        ...  # handle event["data"]
    return "", 200

verify() returns True or raises; construct_event() verifies and returns the parsed event. Both accept tolerance_seconds= (default 300; 0 disables the replay check).

License

MIT © Postpin