OpenAI Assistants API Guide 2025: Build Persistent AI Agents

from openai import OpenAI

client = OpenAI()  # uses OPENAI_API_KEY env var

# 1. Create an Assistant (do this once, save the ID)
assistant = client.beta.assistants.create(
    name="Data Analyst",
    instructions="You are a data analyst. Answer questions about the uploaded CSV files.",
    model="gpt-4o",
    tools=[{"type": "code_interpreter"}, {"type": "file_search"}],
)
print(assistant.id)  # asst_abc123 — save this

# 2. Create a Thread (once per user session)
thread = client.beta.threads.create()

# 3. Add a Message
client.beta.threads.messages.create(
    thread_id=thread.id,
    role="user",
    content="How many rows are in my dataset?",
)

# 4. Stream the Run
with client.beta.threads.runs.stream(
    thread_id=thread.id,
    assistant_id=assistant.id,
) as stream:
    for text in stream.text_deltas:
        print(text, end="", flush=True)

# Upload a file
with open("report.pdf", "rb") as f:
    file = client.files.create(file=f, purpose="assistants")

# Create a vector store and add the file
vector_store = client.beta.vector_stores.create(name="Q1 Reports")
client.beta.vector_stores.files.create(
    vector_store_id=vector_store.id,
    file_id=file.id,
)

# Attach the vector store to the assistant
client.beta.assistants.update(
    assistant_id=assistant.id,
    tool_resources={
        "file_search": {"vector_store_ids": [vector_store.id]}
    },
)