Correct way to json.dump() nested dictionary AND read back into python w/ json.load()?-CodePudding

I have nested dictionaries in "letters" in python. I want to write out all objects to a file so that when the program reruns each dictionary can be imported into the top dictionary "letters" and then appended with additional user inputs/dictionaries.

I think my issue is in not correctly using json.dumps() for each nested dictionary. *I know my dictionary names need to be unique, working on that.

 import json
letter_dict = {}
print('letters dict:', letter_dict)

for number in range(1, 6):
    print('what letter is in position ', number, '?:')
    letter = input()
    if letter == '':
        print('no additional inputs')
        break
    else:
        code = input('what code?:')
        #position = input('what position?:')
    letter_dict['letter'] = letter
    letter_dict['code'] = code
    letter_dict['position'] = number

    print(letter)
    print(code)
    #print(position)
    print(number)
    print(letter_dict)

    with open('letters.txt', 'a') as file:
        dictname = "'dict"   str(number)   "': "
        file.write(dictname)
        file.write(json.dumps(letter_dict))
        file.write(',\n')

letters.txt =

'dict1': {"letter": "a", "code": "y", "position": 1},
'dict2': {"letter": "p", "code": "y", "position": 2},
'dict1': {"letter": "a", "code": "y", "position": 1},

import function:

import json

with open('letters.txt', 'r') as file:
    print(json.load(file))

errors:

  File "/usr/lib/python3.9/json/__init__.py", line 293, in load
    return loads(fp.read(),
  File "/usr/lib/python3.9/json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.9/json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.9/json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

CodePudding user response：

I don't know if it's the problem but your file is not a valid JSON,

You must use double quotes instead of simple
The final comma is not supposed to be there
You must put your dict into curly brackets
Do not duplicate dict keys.

Valid file will be:

{
"dict1": {"letter": "a", "code": "y", "position": 1},
"dict2": {"letter": "p", "code": "y", "position": 2},
"dict3": {"letter": "a", "code": "y", "position": 1}
}

CodePudding user response：

Rather than trying to write yourself a valid json just let the json.dump do the heavy-lifting for you. With a main_dict variable to collect the subdicts, you can just dump it to your file:

import json
main_dict = {}

for number in range(1, 6):
    letter_dict = {}
    letter = input(f'what letter is in position {number}? ')
    if letter:
        code = input('what code?:')
    else:
        print('no additional inputs')
        break
      
    letter_dict['letter'] = letter
    letter_dict['code'] = code
    letter_dict['position'] = number

    main_dict[f'dict{number}'] = letter_dict

with open('letters.json', 'w') as file:
    json.dump(main_dict, file)

Note that I don't open the file letters.txt in append mode because a second run of your program would append another dictionary after the first one, thereby making the json invalid. If you want to append, load the json file in main_dict, add a key-value pair to main_dict and dump again.