INeedToSendAFax Python SDK

Official Python client for the INeedToSendAFax API. Send faxes, track delivery, and verify webhook callbacks.

Using Go? The Go SDK is go get github.com/INeedToSendAFax/sdk-go, source at INeedToSendAFax/sdk-go.

Synchronous Client and AsyncClient
Typed models and exceptions
Automatic idempotency keys and retries
Constant-time webhook signature verification

Install

pip install ineedtosendafax

Quick start

Grab an API key from api.ineedtosendafax.com and set it as IFAX_API_KEY, or pass it to the client.

from ineedtosendafax import Client

client = Client()  # reads IFAX_API_KEY

fax = client.send_fax("15551234567", ["invoice.pdf"])
print(fax.id, fax.status)  # -> queued

Async

import asyncio
from ineedtosendafax import AsyncClient

async def main():
    async with AsyncClient("ifx_live_...") as client:
        fax = await client.send_fax("15551234567", ["invoice.pdf"])
        print(fax.id)

asyncio.run(main())

Sending a fax

send_fax accepts PDF, Word (DOC/DOCX), PNG/JPEG, PostScript, and TIFF, up to 10 combined files and 32 MB each. Files can be paths, bytes, (name, data) tuples, or file objects.

fax = client.send_fax(
    "15551234567",
    ["report.pdf", ("appendix.pdf", open("appendix.pdf", "rb"))],
    callback_url="https://example.com/fax-webhook",
    cover=True,
    cover_text="Confidential",
    sender_name="Acme Billing",
    recipient_name="Dr. Smith",
)

Tracking status

fax = client.get_fax("b1a2c3d4-...")
# fax.status is "queued", "sending", "sent", or "failed".

listing = client.list_faxes(limit=50)   # listing.data, listing.balance_cents
account = client.me()                   # account.balance_cents, account.max_pages, ...
price = client.pricing()                # price.price_cents, ...

Verifying webhooks

When you set callback_url, we POST the final status with an X-Fax-Signature header. Verify it against the raw request body with your webhook signing secret.

from ineedtosendafax import verify_webhook, SignatureVerificationError

def handle(request):
    try:
        event = verify_webhook(
            secret,
            request.headers["X-Fax-Signature"],
            request.get_data(),  # raw, unmodified bytes
        )
    except SignatureVerificationError:
        return "bad signature", 401
    print(event.id, event.status)

verify_webhook uses a 5 minute replay window by default and a constant-time comparison. Pass tolerance=0 to disable the timeout check.

Retries and idempotency

The client retries 429 and 5xx responses and network errors with backoff, honoring Retry-After. send_fax always sends an Idempotency-Key (generated when you do not provide one), so a retried send never delivers a fax twice.

client = Client("ifx_live_...", timeout=90, max_retries=3)

Errors

All non-2xx responses raise a subclass of APIError:

from ineedtosendafax import (
    AuthenticationError,
    InsufficientCreditsError,
    NotFoundError,
    RateLimitError,
    ValidationError,
    ServerError,
)

Each carries .status_code, .code, .message, and .retry_after.

License

MIT

sdk-python