windmill/system_prompts/languages/python3.md

Python

Structure

The script must contain at least one function called main:

def main(param1: str, param2: int):
    # Your code here
    return {"result": param1, "count": param2}

Do not call the main function. Libraries are installed automatically.

Resource Types

On Windmill, credentials and configuration are stored in resources and passed as parameters to main.

You need to redefine the type of the resources that are needed before the main function as TypedDict:

from typing import TypedDict

class postgresql(TypedDict):
    host: str
    port: int
    user: str
    password: str
    dbname: str

def main(db: postgresql):
    # db contains the database connection details
    pass

Important rules:

• The resource type name must be IN LOWERCASE
• Only include resource types if they are actually needed
• If an import conflicts with a resource type name, rename the imported object, not the type name
• Make sure to import TypedDict from typing if you're using it

Imports

Libraries are installed automatically. Do not show installation instructions.

import requests
import pandas as pd
from datetime import datetime

If an import name conflicts with a resource type:

# Wrong - don't rename the type
import stripe as stripe_lib
class stripe_type(TypedDict): ...

# Correct - rename the import
import stripe as stripe_sdk
class stripe(TypedDict):
    api_key: str

Windmill Client

Import the windmill client for platform interactions:

import wmill

See the SDK documentation for available methods.

Preprocessor Scripts

For preprocessor scripts, the function should be named preprocessor and receives an event parameter:

from typing import TypedDict, Literal, Any

class Event(TypedDict):
    kind: Literal["webhook", "http", "websocket", "kafka", "email", "nats", "postgres", "sqs", "mqtt", "gcp"]
    body: Any
    headers: dict[str, str]
    query: dict[str, str]

def preprocessor(event: Event):
    # Transform the event into flow input parameters
    return {
        "param1": event["body"]["field1"],
        "param2": event["query"]["id"]
    }

S3 Object Operations

Windmill provides built-in support for S3-compatible storage operations.

Receiving an S3Object as a script parameter

To accept a file from S3 as input to a script, type the parameter with S3Object (imported from wmill):

import wmill
from wmill import S3Object

def main(file: S3Object):
    content = wmill.load_s3_file(file)
    # ...

S3 operations

import wmill

# Load file content from S3
content: bytes = wmill.load_s3_file(s3object)

# Load file as stream reader
reader: BufferedReader = wmill.load_s3_file_reader(s3object)

# Write file to S3
result: S3Object = wmill.write_s3_file(
    s3object,           # Target path (or None to auto-generate)
    file_content,       # bytes or BufferedReader
    s3_resource_path,   # Optional: specific S3 resource
    content_type,       # Optional: MIME type
    content_disposition # Optional: Content-Disposition header
)