python write json to file

stackoverflow.com › questions › 12309269 › how-do-i-write-json-data-to-a-file

data is a Python dictionary. It needs to be encoded as JSON before writing.

Use this for maximum compatibility (Python 2 and 3):

import json
with open('data.json', 'w') as f:
    json.dump(data, f)

On a modern system (i.e. Python 3 and UTF-8 support), you can write a nicer file using:

import json
with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(data, f, ensure_ascii=False, indent=4)

See json documentation.

Answer from phihag on Stack Overflow

GeeksforGeeks

geeksforgeeks.org › python › reading-and-writing-json-to-a-file-in-python

Reading and Writing JSON to a File in Python - GeeksforGeeks

12:15

It takes two parameters: dictionary: ... · After converting the dictionary to a JSON object, simply write it to a file using the "write" function....

Published August 5, 2025

Stack Overflow

stackoverflow.com › questions › 12309269 › how-do-i-write-json-data-to-a-file

python - How do I write JSON data to a file? - Stack Overflow

Top answer

1 of 16

3348

data is a Python dictionary. It needs to be encoded as JSON before writing.

Use this for maximum compatibility (Python 2 and 3):

import json
with open('data.json', 'w') as f:
    json.dump(data, f)

On a modern system (i.e. Python 3 and UTF-8 support), you can write a nicer file using:

import json
with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(data, f, ensure_ascii=False, indent=4)

See json documentation.

2 of 16

347

To get utf8-encoded file as opposed to ascii-encoded in the accepted answer for Python 2 use:

import io, json
with io.open('data.txt', 'w', encoding='utf-8') as f:
  f.write(json.dumps(data, ensure_ascii=False))

The code is simpler in Python 3:

import json
with open('data.txt', 'w') as f:
  json.dump(data, f, ensure_ascii=False)

On Windows, the encoding='utf-8' argument to open is still necessary.

To avoid storing an encoded copy of the data in memory (result of dumps) and to output utf8-encoded bytestrings in both Python 2 and 3, use:

import json, codecs
with open('data.txt', 'wb') as f:
    json.dump(data, codecs.getwriter('utf-8')(f), ensure_ascii=False)

The codecs.getwriter call is redundant in Python 3 but required for Python 2

Readability and size:

The use of ensure_ascii=False gives better readability and smaller size:

>>> json.dumps({'price': '€10'})
'{"price": "\\u20ac10"}'
>>> json.dumps({'price': '€10'}, ensure_ascii=False)
'{"price": "€10"}'

>>> len(json.dumps({'авгд': 1}))
37
>>> len(json.dumps({'абвгд': 1}, ensure_ascii=False).encode('utf8'))
17

Further improve readability by adding flags indent=4, sort_keys=True (as suggested by dinos66) to arguments of dump or dumps. This way you'll get a nicely indented sorted structure in the json file at the cost of a slightly larger file size.

Discussions

How would you use python to create JSON files?

I read two concrete questions from your post: why you would want to create a JSON object Imagine you want multiple software systems to communicate. Let's say we have three systems, one written in Python, one client written in JavaScript and one more backend system in Java. You can't just send Python objects over a network and expect the systems written in JS or Java to understand them. Same thing the other way around. In the end it's just electrical signals and both the sender and receiver need a common understanding of how to interpret those signals, otherwise they will just be gibberish. That's where data formats like JSON come into play: It's a simple and standardized data format that can be handled in any modern programming language. Now your Python code can serialize its internal representation of a piece of data into this format and send it over a network or store it on some disk, where some other system will eventually pick it up, deserialize it into its own internal representation and process it. show how you would create a JSON object with python import json data = {"year": 2020, "sales": 12345678, "currency": "€"} # creating a JSON string json_string = json.dumps(data) # storing it in a file with open("data.json", "w") as json_file: json.dump(data, json_file) More on reddit.com

r/learnpython

7

5

March 7, 2020

need help understanding how to write a file to json (python) without overwriting it

You cannot append to a json file. You can only read the whole thing into memory, change the data as you need, then overwrite the entire file. (this is how most files work; in real life it's very rare to modify a file) What you have would have done this if you hadn't forgotten the "as f" in open to write part. But also you have too much indentation. Try this: user_id = str(ctx.message.author.id) print(user_id) # reads data with open("test.json", "r") as f: data = json.load(f) print(data) print(type(data)) # checks if user is in data if user_id not in data['users']: # checks if data is type list if type(data) is dict: data = [data] print(type(data)) # updates data with new user data.append({"user_id": user_id}) print(data) # overwrite the json file with new data with open("test.json", "w") as f: json.dump(data, f) More on reddit.com

r/learnpython

6

2

October 4, 2022

How do i save what i write in here to a json file?

How do i save what i write in here to a json file · If you want all of the text, give the start index as '1.0' (line 1, column 0) and the end index as 'end' · Note that after root.mainloop() returns, the widget won’t exist any longer, so here I’m getting it when the window closes: More on discuss.python.org

discuss.python.org

1

0

February 6, 2025

How do I write JSON data to a file in Python? - TestMu AI Community

I have JSON data stored in a dictionary, and I want to write it to a file. I tried the following approach: f = open('data.json', 'wb') f.write(data) However, this results in the error: TypeError: must be string or buffer, not dict How can I correctly save the JSON data to a file in Python? More on community.testmuai.com

community.testmuai.com

0

January 5, 2025

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