JSON Python reading/writing to a json file issue

Question

Code:

import json

numbers = [2, 3, 5, 7, 11, 13]
letters = ["a", "b", "c", "d"]
filename = 'numbers.json'

with open(filename, 'w') as f_obj:
    json.dump(numbers, f_obj)
    json.dump(letters, f_obj)


with open(filename) as f_obj:
    numbers = json.load(f_obj)
    letters = json.load(f_obj)

print(numbers)
print(letters)

I would like to be able to read multiple lists which I have added to a json file and set them as separate lists which can be used later.

I don't mind having to adding a new line between each list in the json file and then reading it in line format.

what is your issue?

Jean-François Fabre
– Jean-François Fabre ♦

2017-10-10 20:18:40 +00:00
Commented Oct 10, 2017 at 20:18 — Jean-François Fabre
– Jean-François Fabre ♦, Commented Oct 10, 2017 at 20:18

PRMoureu · Accepted Answer · 2017-10-10 20:20:25Z

3

why not store them inside a global dictionary ?

import json

numbers = [2, 3, 5, 7, 11, 13]
letters = ["a", "b", "c", "d"]
filename = 'numbers.json'

val={'numbers': numbers, 'letters':letters}

with open(filename, 'w') as f_obj:
    json.dump(val, f_obj)


with open(filename) as f_obj:
    val = json.load(f_obj)
    numbers = val['numbers']
    letters = val['letters']

print(numbers)
print(letters)

answered Oct 10, 2017 at 20:20

PRMoureu

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8 Comments

TIC-FLY Over a year ago

Thank you very much! I was usually scared of using dictionaries so I just used lists for everything but it seems that dictionaries may just be the way forward, thanks again.

PRMoureu Over a year ago

you could also put all the lists inside one global list, but the dictionary makes it easier to retrieve elements by name ( instead of using indexes, and having to remember what index matches each list..)

TIC-FLY Over a year ago

PRMoureu, Could you do this with dictionaries containing dictionaries?

PRMoureu Over a year ago

Sure, you just have to give a key and an object as value, and the value can be many kinds of objects in Python, string, integers, sets, classes, functions, dictionaries ... val={'numbers': numbers, 'letters':letters, 'new_dict':{'a':[1,2,3]}}. Next step : the keys don't need to be strings, you could use integers or other immutable types : val = {1:numbers, 2:letters}... dictionaries are your friends, don't fear them ;-)

TIC-FLY Over a year ago

Sorry but I don't understand the "val={'numbers': numbers, 'letters':letters, 'new_dict':{'a':[1,2,3]}}. " Specifically why's there's so many curly brackets.

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