Musterlösung mit Erklärung

import httpx

BASIS = 'https://jsonplaceholder.typicode.com'


def beitraege_von(client, user_id):
    r = client.get('/posts', params={'userId': user_id})
    r.raise_for_status()
    return r.json()


def beitrag_anlegen(client, titel, text, user_id):
    r = client.post('/posts', json={'title': titel, 'body': text, 'userId': user_id})
    r.raise_for_status()
    return r.status_code, r.json()


def beitrag_holen(client, beitrag_id):
    r = client.get(f'/posts/{beitrag_id}')
    if r.status_code == 404:
        return None
    r.raise_for_status()
    return r.json()


def main():
    with httpx.Client(base_url=BASIS, timeout=10.0) as client:
        posts = beitraege_von(client, 1)
        print(f'{len(posts)} Beiträge')
        for p in posts[:3]:
            print('-', p['title'])

        status, neu = beitrag_anlegen(client, 'Hallo', 'Testbeitrag', 1)
        print('Angelegt:', status, 'id =', neu['id'])

        if beitrag_holen(client, 99999) is None:
            print('Beitrag 99999 nicht gefunden')


if __name__ == '__main__':
    try:
        main()
    except httpx.RequestError as e:
        print('Netzwerkproblem:', e)
    except httpx.HTTPStatusError as e:
        print('Fehlercode vom Server:', e.response.status_code)