How do I add a variable to a JSON list in Python?

Question

I have a JSON file that looks likes this:

{ "users":"John, admin"}

What I want is to be able to add a string into the "users" title. So, basically, I want to allow users to input a new username and add it to this list. Take the following Python code:

newUserInfo = input("Enter a new username: ")

And then say I input "Michael" Then the JSON file should look like this:

{ "users":"John, admin, Michael"}

I've tried the following:

with open(userFile, "a") as userobj:
newUserInfo = json.dump(allUserInfo["users": newUserInfo], userobj)

And It returns an error. Is there an easy way to do this?

Thanks in advance.

You are aware that {"users": ["John", "admin"]} would be a much besser format? — Klaus D.
– Klaus D., Commented Oct 20, 2018 at 4:44

Mark Tolonen · Accepted Answer · 2018-10-20 04:58:05Z

1

Append the name to the string:

import json
s = '''{"users":"John, admin"}'''
data = json.loads(s)
newUserInfo = input("Enter a new username: ")
data['users'] += ', ' + newUserInfo
s2 = json.dumps(data)
print(s2)

Output:

{"users": "John, admin, Michael"}

But a more natural way to use JSON would be represent the names in a list:

import json

s = '''{"users":["John","admin"]}'''

data = json.loads(s)
newUserInfo = input("Enter a new username: ")
data['users'].append(newUserInfo)
s2 = json.dumps(data)
print(s2)

Output:

{"users": ["John", "admin", "Michael"]}

answered Oct 20, 2018 at 4:58

Mark Tolonen

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1 Comment

Michael Over a year ago

Awesome. Thanks for your help!

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