The DeepSeek API and the open weights and your first script

The concept

DeepSeek serves its models over an API that is compatible with the OpenAI request shape and priced far below the frontier labs, and publishes the weights of its core models. The idea is simple: the same model you have been chatting with also answers a web request, so you can put it inside a script, a spreadsheet or a page. A key identifies you; a request sends the text; a response comes back as data.

The reason to try it once, even if you never build anything: it makes the chat version less mysterious. You see that the whole conversation is text in and text out, that your instructions are literally lines of a request, and that "the model" is one parameter among several.

A first call looks like this:

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_DEEPSEEK_KEY",
    base_url="https://api.deepseek.com",
)

r = client.chat.completions.create(
    model="deepseek-reasoner",
    messages=[{"role": "user", "content": "A train covers 240 km in 3h20m. What is its speed in m/s? Show every step."}],
)

print(r.choices[0].message.content)