When I add a identifier to a dictionary in my python project it works properly however when I try saving my dictionary with json it does not save as I can see in the .txt file.

My code:

import json

def read_file(file):
    f = open(file, "r")
    file_contents = f.read()
    f.close()
    return(file_contents)

def write_file(file, content):
    f = open(file, "w")
    f.write(json.dumps(content))
    f.close()


data = {

}


data["user1"] = "100"

write_file("data.txt", data)
file_contents = read_file("data.txt")
print(file_contents)

data["user1"] = "150"

write_file("data.txt", data)
file_contents = read_file("data.txt")
print(file_contents)

I tried changing the code a bit however I would get different errors including an error saying you cant add item identifiers to a str.