How to resolve a LID in Python with the Wapito WhatsApp API

Before you start

• pip install requests
• os.environ["WAPITO_TOKEN"]
• A channel with a WhatsApp number linked to it, and its API token. Create one in the dashboard — the authentication guide shows where the token goes.

The whole script

Every step above in one runnable file. Save it as lid-to-phone.py, put your token in the environment, and run it.

"""LID to Phone with the Wapito WhatsApp API.

Resolve the identities you already know, resolve the ones that arrive in events, and design for the case where no phone number comes back.

Run it with:
    export WAPITO_TOKEN="wpt_..."
    python lid-to-phone.py
"""
import os

import requests

BASE_URL = "https://api.wapito.com/v1"
TOKEN = os.environ["WAPITO_TOKEN"]

# --- Look up the LID for a number you know ---
url = BASE_URL + "/contacts/+15551234567/lid"

headers = {"Authorization": "Bearer " + TOKEN}

response = requests.get(url, headers=headers)

print(response.json())

# --- Resolve a LID that arrived in an event ---
url = BASE_URL + "/contacts/lid/187264518273645@lid"

headers = {"Authorization": "Bearer " + TOKEN}

response = requests.get(url, headers=headers)

print(response.json())

Receive the webhook

FastAPI receiver for groups.participants, messages — it verifies the signature, answers immediately and does the work after. Install it with pip install fastapi uvicorn and save it as webhook.py.

import hashlib
import hmac
import os
import time

from fastapi import FastAPI, Header, HTTPException, Request

app = FastAPI()
SECRET = os.environ["WAPITO_WEBHOOK_SECRET"].encode()
EVENTS = ["groups.participants", "messages"]


def verify(raw: bytes, header: str | None) -> bool:
    """Checks the X-Wapito-Signature header: t=<ms>,v1=<hex hmac-sha256>."""
    if not header:
        return False
    parts = dict(p.split("=", 1) for p in header.split(",") if "=" in p)
    ts, sig = parts.get("t"), parts.get("v1")
    if not ts or not sig:
        return False
    if abs(time.time() * 1000 - int(ts)) > 300_000:  # 5 minute clock skew
        return False
    expected = hmac.new(SECRET, ts.encode() + b"." + raw, hashlib.sha256).hexdigest()
    return hmac.compare_digest(expected, sig)


@app.post("/wapito")
async def wapito(request: Request, signature: str | None = Header(default=None, alias="X-Wapito-Signature")):
    raw = await request.body()
    if not verify(raw, signature):
        raise HTTPException(status_code=401, detail="bad signature")
    payload = await request.json()
    if payload["event"] in EVENTS:
        print(payload["event"], payload["data"])
    return {"ok": True}  # answer 2xx fast; do the real work in a queue

Gotchas

• requests does not raise on a 4xx by itself. Call response.raise_for_status() or check response.ok, otherwise a 429 send_rate_limited silently looks like a successful send and your loop keeps hammering the queue.
• json= and data= are not interchangeable. Pass json={...} so requests sets Content-Type: application/json and encodes UTF-8 for you; data= with a dict sends form encoding and the API answers 400 invalid_request.
• The default requests timeout is None, which means a stalled connection hangs your worker forever. Always pass timeout=(5, 30) and treat a read timeout as "maybe delivered" - re-check with the message id before you send again.
• A group id such as 120363000000000000@g.us is a string, not a number. Building it with an f-string from an int drops the precision and you get 404 not_found.
• Emoji and accented text need no extra work in Python 3, but reading a CSV of numbers with the default encoding on Windows will mangle them - open files with encoding="utf-8".

Where to run it

• Google Cloud Run (container, scale to zero, one revision per deploy)
• Render background worker for the sender, Render web service for the webhook receiver
• A 1 GB VPS with systemd for the worker and Caddy in front of the FastAPI receiver
• AWS Lambda + API Gateway for the webhook receiver only (the sender needs a long-lived process for queue spacing)

Pitfalls in Python

• A dataclass with phone: str rather than str | None will be constructed with None at runtime anyway and only mypy will complain later; declare the field Optional from the start and let the type checker enforce it across the receiver and the batch script alike.
• An lru_cache around a function that raises on 404 caches nothing for that identity and re-requests it on every event; cache the None result explicitly in your own dict, or return None from the wrapped function instead of letting the exception escape.
• SQLAlchemy's session.merge on a model whose primary key is the phone column will insert a second row for the same identity the first time a phone arrives after a null; make the identity the primary key and give the phone a plain nullable index instead.

Frequently asked questions

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