Python REST API Example with CRUD

A Small, Complete API

Time to assemble the pieces: a users API with the five classic endpoints —

POST /users create · GET /users list · GET /users/{id} read one · PUT /users/{id} replace · DELETE /users/{id} remove.

The store is an in-memory dict, so the example stays self-contained. (A real server handles requests concurrently, so a production version would guard the dict with a lock and probably swap it for a database — the handlers would not change shape.)

Create and List

POST parses the incoming JSON, gives the user an id, stores it, and answers 201 with the created record — id included, so the client learns it. GET returns everyone as a JSON array.

POST /users and GET /users

Two creations, then the list: each POST answers 201 with the stored user, and the final GET shows both — the API's state grew with each request.

Write a Python program implementing the create and list part of a users REST API over an in-memory dict: POST /users parses JSON, assigns an id and answers 201 with the created user; GET /users answers with the JSON array of all users. Serve on a free port, create Ana and Ben, list them, and print every status and body.

> Output: complete Python program

Prompt

Write a Python program implementing the create and list part of a users REST API over an in-memory dict: POST /users parses JSON, assigns an id and answers 201 with the created user; GET /users answers with the JSON array of all users. Serve on a free port, create Ana and Ben, list them, and print every status and body.

Output: complete Python program

import json
import threading
import urllib.request
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer

users = {}
next_id = 1

class UsersHandler(BaseHTTPRequestHandler):
  def do_POST(self):
    global next_id
    length = int(self.headers.get("Content-Length", 0))
    try:
      data = json.loads(self.rfile.read(length))
    except json.JSONDecodeError:
      self.reply(400, {"error": "invalid JSON"})
      return
    user = {"id": next_id, "name": data["name"]}
    users[next_id] = user
    next_id += 1
    self.reply(201, user)

  def do_GET(self):
    self.reply(200, [users[k] for k in sorted(users)])

  def reply(self, status, data):
    self.send_response(status)
    self.send_header("Content-Type", "application/json")
    self.end_headers()
    self.wfile.write((json.dumps(data) + "\n").encode())

  def log_message(self, fmt, *args):
    pass

server = ThreadingHTTPServer(("127.0.0.1", 0), UsersHandler)
base = f"http://127.0.0.1:{server.server_address[1]}"
threading.Thread(target=server.serve_forever, daemon=True).start()

for name in ["Ana", "Ben"]:
  payload = json.dumps({"name": name}).encode()
  req = urllib.request.Request(base + "/users", data=payload,
                               headers={"Content-Type": "application/json"})
  with urllib.request.urlopen(req) as resp:
    print("POST /users ->", resp.status, resp.read().decode().strip())

with urllib.request.urlopen(base + "/users") as resp:
  print("GET  /users ->", resp.status, resp.read().decode().strip())

server.shutdown()

Read One, Replace, Delete

The /users/{id} routes complete the set: read answers 200 or 404, replace parses the new data into the existing id, delete answers 204. After the delete, the same GET that worked before honestly returns 404 — the resource is gone.

GET, PUT and DELETE on /users/{id}

The full life of one resource: read it, replace it (the response carries the new name), delete it, and fail to read it — every step with the correct status code.

Write a Python program implementing GET, PUT and DELETE for /users/{id} over an in-memory dict seeded with one user: GET answers 200 or 404 with JSON, PUT replaces the user keeping the id, DELETE answers 204. Serve on a free port and run the full lifecycle — read, replace, delete, read again — printing each method, status and body.

> Output: complete Python program

Prompt

Write a Python program implementing GET, PUT and DELETE for /users/{id} over an in-memory dict seeded with one user: GET answers 200 or 404 with JSON, PUT replaces the user keeping the id, DELETE answers 204. Serve on a free port and run the full lifecycle — read, replace, delete, read again — printing each method, status and body.

Output: complete Python program

import json
import threading
import urllib.error
import urllib.request
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer

users = {1: {"id": 1, "name": "Ana"}}

class UserHandler(BaseHTTPRequestHandler):
  def user_id(self):
    return int(self.path.rsplit("/", 1)[-1])   # "/users/1" -> 1

  def do_GET(self):
    user = users.get(self.user_id())
    if user is None:
      self.reply(404, {"error": "user not found"})
    else:
      self.reply(200, user)

  def do_PUT(self):
    length = int(self.headers.get("Content-Length", 0))
    data = json.loads(self.rfile.read(length))
    user = {"id": self.user_id(), "name": data["name"]}   # keep the id
    users[self.user_id()] = user
    self.reply(200, user)

  def do_DELETE(self):
    users.pop(self.user_id(), None)
    self.send_response(204)
    self.end_headers()

  def reply(self, status, data):
    self.send_response(status)
    self.send_header("Content-Type", "application/json")
    self.end_headers()
    self.wfile.write((json.dumps(data) + "\n").encode())

  def log_message(self, fmt, *args):
    pass

server = ThreadingHTTPServer(("127.0.0.1", 0), UserHandler)
base = f"http://127.0.0.1:{server.server_address[1]}"
threading.Thread(target=server.serve_forever, daemon=True).start()

def call(method, path, payload=None):
  data = payload.encode() if payload else None
  req = urllib.request.Request(base + path, data=data, method=method,
                               headers={"Content-Type": "application/json"})
  try:
    with urllib.request.urlopen(req) as resp:
      status, body = resp.status, resp.read().decode()
  except urllib.error.HTTPError as err:
    status, body = err.code, err.read().decode()
  print(f"{method:<6} {path} -> {status} {body.strip()}".rstrip())

call("GET", "/users/1")
call("PUT", "/users/1", '{"name": "Ana Maria"}')
call("DELETE", "/users/1")
call("GET", "/users/1")

server.shutdown()