Diff json files and write changes

Question

Using python I'm trying to diff two json files, update if there's a difference.

I have a rough draft going but haven't found out how to update my file!

import json
import sys
import jsondiff as jd
from jsondiff import diff


one="$1"
two="$2"

def compare_json(one, two) :

    with open(one, "r") as f, open(two, "r") as f2:
        file_one=json.load(f)
        file_two=json.load(f2)
        differences = diff(file_one, file_two, syntax='explicit')
        print(differences)
        update = differences[jd.update]
        print(update)
        insert = differences[jd.insert]
        print(insert)
        delete = differences[jd.delete]
        print(delete)

if __name__ == "__main__":
   compare_json(sys.argv[1],sys.argv[2])

I can get the differences but I haven't figure out a good way in updating the file.

My end goal is this:

diffy = diff(file_one,file_two)
if diffy
    update file_two

I only want to update values that are different in file two.

For example:

file one:

{ "type": "secure"
  "secure": {
    "id": "123",
    "client": "google"
  }
}

file two:

{ "type": "secure"
  "secure": {
    "id": "456",
    "client": "google"
  }
}

So the only difference between the files is the value of secure["id"]. I would like to update the value of secure["id"] in file two to the value of secure["id"] in file one. (Basically making file one equal to file two without rewriting everything in the file)

Any suggestions how to do this cleanly?

Does this answer your question? [How to open a file for both reading and writing?](https://stackoverflow.com/questions/6648493/how-to-open-a-file-for-both-reading-and-writing) — Jan Wilamowski, Sep 09 '22 at 02:44
So in the end you want that file 2 is identical to file 1. Calculating the differences is pointless, just make a copy of file 1. — mkrieger1, Sep 09 '22 at 15:07

score 0 · Accepted Answer · answered Sep 21 '22 at 18:23

Sorry for the late response.. deadlines at work...

I ended up going with jsondiff

Here's a sample code snippet (without any exception handling):

   import jsondiff as jd
   from jsondiff import diff
   
   # open and load files
   with open(one, "r") as f, open(two, "r") as f2:
       file_one = json.load(f)
       file_two = json.load(f2)
       
       # get differences in file_two (file_one being the master)  
       differences = (file_two, file_one)
       
       # in order to access $update from differences use jd.update
       update = differences[jd.update]
       
       # assuming there are updates, loop through and update them accordingly
       for x in update:
           file_two.update({x : update[x]})

       
       # Open a new file and write the updated contents of file_two 
       outfile = open(outfile, "w")
       json.dump(file_two, outfile, indent=4)

Turns out it wasn't too bad once using jsondiff and understanding how to access the objects returned

Diff json files and write changes

1 Answers1