When I remove an object from an array in json with python, it ruins my json file. How do I fix this?

Question

when I remove an object from an array in json with python, it ruins my json file. For example here is my python:

srs = server["purchaseableRoles"]
                        if srs == []:
                            await ctx.send("Your server has no purchaseable roles at the moment, you cant remove one.")
                        else:
                            for i in srs:
                                splitsrs = i.split("|")
                                if int(splitsrs[0]) == role.id:
                                    print(str(i))
                                    srs.remove(str(i))
                                    print(srs)
                                    f.seek(0)
                                    json.dump(serversjson,f,sort_keys=True,indent=4)
                                    await ctx.send("removed the role from the role shop!")

(please ignore the discord.py stuff, its in a discord bot. Also ignore the weird indents I don't know why it pasted in like that) That code is pretty much removing an object from an array in a json file, and updating it. Except for when I do that, here is my json:

{
    "servers": [
        {
            "id": 1234,
            "purchaseableRoles": [
                "1234|5678"
            ]
        },
        {
            "id": 813070255127396352,
            "purchaseableRoles": []
        }
    ]
}071595911774238|5"
            ]
        }
    ]
}

it just gets all messed up. Here was my json before the mess-up:

{
    "servers": [
        {
            "id": 1234,
            "purchaseableRoles": [
                "1234|5678"
            ]
        },
        {
            "id": 813070255127396352,
            "purchaseableRoles": [
                "813071595911774238|5"
            ]
        }
    ]
}

is there a way to prevent this? Thanks in advance if you help.

Badly indented python code is invalid python code!. Please fix your indentation. Also, please post a minimal reproducible example that people can run to reproduce your problem. Simply pasting your code here isn't acceptable. You need to put in some effort to convert it to a minimal reproducible example so that the people helping you can run that code easily — pho
– pho, Commented Feb 23, 2021 at 17:12
Does this answer your question? How to erase the file contents of text file in Python? — pho
– pho, Commented Feb 23, 2021 at 17:14
the linked duplicate says exactly what your accepted answer does. Why the sarcasm? — pho
– pho, Commented Feb 23, 2021 at 18:44

C14L · Accepted Answer · 2021-02-23 17:23:34Z

2

You are moving the file cursor to the begining of the file and overwrite the Bytes in the file with Bytes in the JSON string.

But you removed some stuff, so the string that overwrites the file is shorter than the string in the file.

So at the end of the file, some of the old string remains.

There is a method file_obj.truncate(). But there is little documentation on it in Python3, apparently. Something like this:

f.seek(0)
f.truncate()

edited Feb 23, 2021 at 17:23

answered Feb 23, 2021 at 17:12

C14L

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3 Comments

HoneyPoop Over a year ago

Thanks, that helped. How would I fix this?

C14L Over a year ago

I added it to the answer.

HoneyPoop Over a year ago

thanks! ill look at the docs and accept this answer once i test it.

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