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Examples

​​ Return a custom status code and/or response headers

src/entry.py
from js import Response, Headers
async def on_fetch(request, env):
# Create a Headers object
headers = Headers.new({"x-hello-from": "python-workers"}.items())
# Return a response object with a status code and headers
return Response.new("Hello world!", status=404, headers=headers)

​​ Parse an incoming request URL

src/entry.py
from js import Response, Headers
from urllib.parse import urlparse, parse_qs
async def on_fetch(request, env):
# Parse the incoming request URL
url = urlparse(request.url)
# Parse the query parameters into a Python dictionary
params = parse_qs(url.query)
if "name" in params:
greeting = "Hello there, {name}".format(name=params["name"][0])
return Response.new(greeting)
if url.path == "/favicon.ico":
return Response.new("")
return Response.new("Hello world!")

​​ Parse JSON from the incoming request

src/entry.py
from js import Response
async def on_fetch(request):
name = (await request.json()).name
return Response.new("Hello, {name}".format(name=name))

​​ Emit logs from your Python Worker

src/entry.py
# To use the JavaScript console APIs
from js import console
# To use the native Python logging
import logging
async def on_fetch(request):
# Use the console APIs from JavaScript
# https://developer.mozilla.org/en-US/docs/Web/API/console
console.log("console.log from Python!")
# Alternatively, use the native Python logger
logger = logging.getLogger(__name__)
# The default level is warning. We can change that to info.
logging.basicConfig(level=logging.INFO)
logger.error("error from Python!")
logger.info("info log from Python!")
# Or just use print()
print("print() from Python!")
return Response.new("We're testing logging!")

​​ Respond with JSON

src/entry.py
from js import Response, Headers
import json
async def on_fetch(request):
# Use json.loads to serialize Python objects to JSON strings
payload = json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True)
headers = Headers.new({"content-type": "application/json"}.items())
return Response.new(payload, headers=headers)

​​ Publish to a Queue

src/entry.py
from js import Response, Object
from pyodide.ffi import to_js as _to_js
# to_js converts between Python dictionaries and JavaScript Objects
def to_js(obj):
return _to_js(obj, dict_converter=Object.fromEntries)
async def on_fetch(request, env):
# Bindings are available on the 'env' parameter
# https://developers.cloudflare.com/queues/
# The default contentType is "json"
# We can also pass plain text strings
await env.QUEUE.send("hello", contentType="text")
# Send a JSON payload
await env.QUEUE.send(to_js({"hello": "world"}))
# Return a response
return Response.json(to_js({"write": "success"}))

​​ Next steps