I'm trying a deduct a value in json but since it take away a digit a problem occurs-CodePudding

Sounds easy but I've been trying to find a fix for this problem but I would like to know if there is any fix at all.

with open('py.json','r ',encoding='utf-8') as f:
    data = json.load(f)
    f.seek(0)
    data['numbers'][0]['value'] = data['numbers'][0]['value']-1
    json.dump(data, f, indent=4)

Before:

{
    "numbers": [
        {
            "value": 10
        }
    ]
}

A simple way of adding or (in this case) subtracting an int as a value. The value starts off as 10. This is what happens after the code is ran.

After:

{
    "numbers": [
        {
            "value": 9
        }
    ]
}}

An extra "}" is placed at the end of the file, seemingly filling in for the missing digit for the number 10. The weird thing is that if I print "data", all curly brackets are closed. How can I get rid of that one extra bracket?

CodePudding user response：

Call f.truncate() after writing to clear old content that remains after the end of the new written content

with open('py.json','r ',encoding='utf-8') as f:
    data = json.load(f)
    f.seek(0)
    data['numbers'][0]['value'] = data['numbers'][0]['value']-1
    json.dump(data, f, indent=4)
    f.truncate()