Exercise: Write User Records To JSON File

Documentation

• json module

Plan

Lets add more functionality to our userdb module. In Exercise: Split Strings To User Dictionaries, we have read user records of the form

{
    'id': 666,      # <-- int
    'firstname': 'Jörg',
    'lastname': 'Faschingbauer',
    'birth': '1966-06-19',
}

Now, given that we can have a list - an iterable to be exact - of such records, lets write them out in JSON format (see here, watch out for functions like load(), loads(), dump(), and dumps()).

Again, download the test below which contains the requirements. Read carefully, and note that the function writes the user records to something that looks like a file (the test uses io.StringIO which is not a file but behaves like one).

code/test_write_userdicts_to_json.py

import userdb
import io
import json

def test_write_users_to_json():
    users_out = [
        {
            'id': 666,
            'firstname': 'Jörg',
            'lastname': 'Faschingbauer',
            'birth': '1966-06-19',
        },
        {
            'id': 42,
            'firstname': 'Caro',
            'lastname': 'Faschingbauer',
            'birth': '1997-04-25',
        },
        {
            'id': 7,
            'firstname': 'Johanna',
            'lastname': 'Faschingbauer',
            'birth': '1995-06-11',
        },
        {
            'id': 1024,
            'firstname': 'Philipp',
            'lastname': 'Lichtenberger',
            'birth': '1986-04-06',
        },
    ]

    output = io.StringIO()                             # <-- file-like, for output
    userdb.write_users_to_json(users_out, output)

    input = io.StringIO(output.getvalue())             # <-- file-like, for input
    users_in = json.load(input)

    assert users_out[0] == users_in[0]
    assert users_out[1] == users_in[1]
    assert users_out[2] == users_in[2]
    assert users_out[3] == users_in[3]