Append list of Python dictionaries to a file without loading it

Question

Suppose I need to have a database file consisting of a list of dictionaries:

file:

[
  {\"name\":\"Joe\",\"data\":[1,2,3,4,5]},
  {   ...                         


        

Answer 1

Using the same approach as user3500511...

Suppose we have two lists of dictionaries (dicts, dicts2). The dicts are converted to json formatted strings. Dicts is saved to a new file - test.json. Test.json is reopened and the string objects are formatted with the proper delimiters. With the reformatted objects, dict2 can be appended and the file still maintains the proper structure for a JSON object.

import json

dicts = [{ "name": "Stephen", "Number": 1 }
         ,{ "name": "Glinda", "Number": 2 }
         ,{ "name": "Elphaba", "Number": 3 }
         ,{ "name": "Nessa", "Number": 4 }]

dicts2= [{ "name": "Dorothy", "Number": 5 }
         ,{ "name": "Fiyero", "Number": 6 }]


f = open("test.json","w")
f.write(json.dumps(dicts))
f.close()

f2 = open("test.json","r+")
f2.seek(-1,2)
f2.write(json.dumps(dicts2).replace('[',',',1))
f2.close()

f3 = open('test.json','r')
f3.read()