How to store JSON.(discord.py) - discord.py

Question

So I tried storing a variable to a json file,but it gives me this error:
Object of type Command is not JSON serializable
The code something like this:
import discord
from discord.ext import commands
import json
num = 0
def store():
with open("num.json", 'w') as file:
json.dump(num, file)
bot = commands.Bot(command_prefix='!')
#bot.command()
async def increase():
num += 1
await ctx.send("I increased your number,now it is: " + num)
store()

Answer 1

Object of type Command is not JSON serializable says, that variable (or entity) you provided can't be transformed (serialized) into the JSON format.
In your case that is because you haven't follow key:value json rule. JSON is similar to the Python's dict (except keys can only be strings). So to be able to store your variable, you have to pass it to the json.dump function as following: {"my_var": num}.
So simply change your code to something like that:
def store():
with open("num.json", 'w') as file:
json.dump({"num": num}, file) #HERE'S THE DEAL! ENTITY SHOULD BE DICT!
bot = commands.Bot(command_prefix='!')
#bot.command()
async def increase():
num += 1
await ctx.send("I increased your number,now it is: " + num)
store()

Answer 2

You didnt open the json file, so you cant write to it.
try this:
num = 0
#bot.command()
async def increase():
num += 1
#opening the json
with open("num.json", "r") as file:
x = json.load(file)
#setting the number
x["num"] = num
#now store it
with open("num.json", "w") as file:
json.dump(file, x, indent=4)
await ctx.send("I increased your number,now it is: " + num)
the num.json should like this (before running the command):
{
"num": 0
}