追加到 json、python 中的字典文件

Question

So I have a file python_dictionary.json which contains a dictionary which I want to append to without having to open each time. Let's say that python_dictionary.json contains only:

{
    key1: value`
}

and I want to add

new_dictionary=
    {
        key2:value2
    }

Right now I am doing:

with open('python_dictionary.json','a') as file:
    file.write(json.dumps(new_dictionary,indent=4))

This creates a dictionary as:

{
    key1:value1
}
{
    key2:value2
}

which is obviously not a real dictionary.

I am aware of this: Add values to existing json file without rewriting it

but this deals with adding a single entry, I want to do a json.dumps

Answer 1

Sounds like you want to load a dictionary from json, add new key values and write it back. If that's the case, you can do this:

with open('python_dictionary.json','r+') as f:
    dic = json.load(f)
    dic.update(new_dictionary)
    json.dump(dic, f)

(mode is 'r+' for reading and writing, not appending because you're re-writing the entire file)

If you want to do the append thing, along with json.dumps, I guess you'd have to remove the first { from the json.dumps string before appending. Something like:

with open('python_dictionary.json','a') as f:
    str = json.dumps(new_dictionary).replace('{', ',', 1)
    f.seek(-2,2)
    f.write(str)

Answer 2

When the 'r+' or 'a' option does not work properly, you can do the following:

with open('python_dictionary.json','r') as f:
    dic = json.load(f)

dic.update(new_dictionary)

with open('python_dictionary.json','w') as f:
    json.dump(dic, f)

The first part read the existing dictionary. Then you update the dictionary with the new dictionary. Finally, you rewriting the whole updated dictionary.