How to beginner · 3 min read

How to use DeepSeek function calling

Q: How to use DeepSeek function calling

Use the OpenAI Python SDK with base_url="https://api.deepseek.com" to call DeepSeek's deepseek-chat model. Pass your function definitions in the functions parameter and handle the function_call response to execute or process the function output.

Quick answer

Use the OpenAI Python SDK with base_url="https://api.deepseek.com" to call DeepSeek's deepseek-chat model. Pass your function definitions in the functions parameter and handle the function_call response to execute or process the function output.

PREREQUISITES

Python 3.8+
DeepSeek API key
pip install openai>=1.0

Setup

Install the openai Python package and set your DeepSeek API key as an environment variable. Use the OpenAI client with the base_url set to DeepSeek's API endpoint.

bash

pip install openai>=1.0

Step by step

This example demonstrates how to call DeepSeek's deepseek-chat model with function calling enabled. Define your functions, send them in the request, and handle the function call response.

python

import os
from openai import OpenAI

client = OpenAI(api_key=os.environ["DEEPSEEK_API_KEY"], base_url="https://api.deepseek.com")

functions = [
    {
        "name": "get_current_weather",
        "description": "Get the current weather in a given location",
        "parameters": {
            "type": "object",
            "properties": {
                "location": {"type": "string", "description": "The city and state, e.g. San Francisco, CA"},
                "unit": {"type": "string", "enum": ["celsius", "fahrenheit"]}
            },
            "required": ["location"]
        }
    }
]

messages = [
    {"role": "user", "content": "What's the weather like in New York?"}
]

response = client.chat.completions.create(
    model="deepseek-chat",
    messages=messages,
    functions=functions,
    function_call="auto"
)

choice = response.choices[0]
message = choice.message

if message.get("function_call"):
    function_name = message["function_call"]["name"]
    function_args = message["function_call"]["arguments"]
    print(f"Function to call: {function_name}")
    print(f"Arguments: {function_args}")
else:
    print(message.content)

output

Function to call: get_current_weather
Arguments: {"location": "New York"}

Common variations

You can specify function_call as "none" to disable function calling or provide a specific function name to force calling. Use different DeepSeek models like deepseek-reasoner by changing the model parameter. Async calls require custom HTTP clients as the OpenAI SDK does not natively support async for DeepSeek.

Troubleshooting

If you get authentication errors, verify your DEEPSEEK_API_KEY environment variable is set correctly.
If function calls are not triggered, ensure your functions parameter is correctly formatted as a list of JSON schema objects.
Check network connectivity to https://api.deepseek.com if requests time out.

✅

Key Takeaways

Use the OpenAI SDK with base_url="https://api.deepseek.com" to access DeepSeek APIs.
Pass function definitions in the functions parameter to enable function calling.
Handle the function_call field in the response to execute or process functions.
Specify function_call="auto" to let the model decide when to call functions.
Verify environment variables and JSON schema formatting to avoid common errors.

Verified 2026-04 · deepseek-chat, deepseek-reasoner

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