Parse JSON API

Python · Example / how-to

📋 Overview

Fetch a JSON API with urllib or httpx, validate the shape lightly, and extract fields safely.

🔧 Core concepts

Piece	Role
GET + JSON body	Typical REST read
`response.json()`	Decode payload
Key checks	Avoid `KeyError` on partial data
Timeout	Fail fast on hung networks

💡 Examples

parse_json_api.py (stdlib):

from __future__ import annotations

import json
import urllib.error
import urllib.request
from typing import Any


def fetch_user(user_id: int, timeout: float = 10.0) -> dict[str, Any]:
    url = f"https://jsonplaceholder.typicode.com/users/{user_id}"
    req = urllib.request.Request(url, headers={"Accept": "application/json"})
    try:
        with urllib.request.urlopen(req, timeout=timeout) as resp:
            raw = resp.read().decode("utf-8")
    except urllib.error.HTTPError as e:
        raise RuntimeError(f"HTTP {e.code} for user {user_id}") from e
    except urllib.error.URLError as e:
        raise RuntimeError(f"network error: {e.reason}") from e

    data = json.loads(raw)
    if not isinstance(data, dict):
        raise ValueError("expected a JSON object")
    if "id" not in data or "email" not in data:
        raise ValueError("missing id or email")
    return data


def main() -> None:
    user = fetch_user(1)
    print(f"{user['name']} <{user['email']}>")


if __name__ == "__main__":
    main()

With httpx (optional):

import httpx

def fetch_user_httpx(user_id: int) -> dict:
    r = httpx.get(
        f"https://jsonplaceholder.typicode.com/users/{user_id}",
        timeout=10.0,
    )
    r.raise_for_status()
    return r.json()

⚠️ Pitfalls

Never assume every key exists — APIs change and error bodies differ.
Always set a timeout; default can hang forever.
json.loads on HTML error pages raises JSONDecodeError — catch it.

Parse JSON API

Parse JSON API

📋 Overview

🔧 Core concepts

💡 Examples

⚠️ Pitfalls

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