opensend Python SDK

Minimal first-party Python SDK for OpenSend transactional email sends with a Resend-shaped API surface.

Use your OpenSend API key (os_...) with the Resend-compatible API surface.

Installation

This package is staged for future PyPI publishing. From this repository today:

bash

python -m pip install ./packages/python-sdk

After publication, the intended package install is:

bash

python -m pip install opensend

Setup

Use an environment variable instead of hardcoding API keys:

bash

export OPENSEND_API_KEY="os_your_api_key"

For self-hosted OpenSend, point the SDK at your deployment origin. The default hosted origin is https://api.opensend.com.

bash

export OPENSEND_BASE_URL="http://localhost:3015"

Send an email

The module-level surface mirrors Resend's Python ergonomics:

python

import os
import opensend

opensend.api_key = os.environ["OPENSEND_API_KEY"]
opensend.base_url = os.environ.get("OPENSEND_BASE_URL", opensend.DEFAULT_BASE_URL)

params: opensend.Emails.SendParams = {
    "from": "hello@yourdomain.com",
    "to": "recipient@example.com",
    "subject": "Hello from OpenSend",
    "html": "# It works!",
}

email = opensend.Emails.send(params)
print(email["id"])

Python reserves from as a keyword argument name, but dictionary keys can still use the OpenSend/Resend JSON field name. If you prefer constructing dictionaries with Python identifiers, the SDK also accepts from_ or from_email and sends that value as JSON from.

python

params: opensend.SendParams = {
    "from_": "hello@yourdomain.com",
    "to": ["recipient@example.com"],
    "subject": "Hello from OpenSend",
    "text": "It works!",
}

Batch send

python

result = opensend.Emails.send_batch([
    {
        "from": "hello@yourdomain.com",
        "to": "a@example.com",
        "subject": "Hi A",
        "html": "
A
",
    },
    {
        "from": "hello@yourdomain.com",
        "to": "b@example.com",
        "subject": "Hi B",
        "html": "
B
",
    },
])

print(result["data"])

Instance client

python

from opensend import OpenSend

client = OpenSend(
    os.environ["OPENSEND_API_KEY"],
    base_url=os.environ.get("OPENSEND_BASE_URL", "https://api.opensend.com"),
)

email = client.emails.send({
    "from": "hello@yourdomain.com",
    "to": "recipient@example.com",
    "subject": "Hello from OpenSend",
    "html": "# It works!",
})

Resend is also exported as an alias class for migration-oriented code:

python

from opensend import Resend

client = Resend(os.environ["OPENSEND_API_KEY"], base_url="http://localhost:3015")

Errors

Non-2xx API responses raise opensend.OpenSendError (also exported as opensend.ApiError). The exception keeps OpenSend's public error envelope fields when present.

python

try:
    opensend.Emails.send(params)
except opensend.OpenSendError as error:
    print(error.status_code, error.code, error.message, error.details)

Supported first slice

opensend.Emails.send(params) → POST /emails
opensend.Emails.send_batch(params) → POST /emails/batch
Bearer API key auth
Configurable base URL
Optional idempotency_key= request header
Typed request/response structures for transactional email sends

This first package intentionally does not implement the full Resend resource surface yet.

Tests

bash

python -m unittest discover packages/python-sdk/tests