How can I suppress newlines within an output array when dumping indented JSON?

Question

I have this code:

import json

my_list = [1, 2, 3]
my_dict = {"key": "value", "boolean": True}
my_json = {"object": my_dict, "array": my_list}

print(json.dumps(my_json, indent=4))

I get an output like:

{
    "object": {
        "key": "value",
        "boolean": true
    },
    "array": [
        1,
        2,
        3
    ]
}

I want it the elements of the "array" array to appear on the same line, like so:

{
    "object": {
        "key": "value",
        "boolean": true
    },
    "array": [1, 2, 3]
}

How can I get this result?

I guess you could use regex to search & replace. But how do you want to handle more complex JSON that contains lists & dicts nested inside other lists & dicts? To get complete control you can implement your own class that inherits from json.JSONEncoder. — PM 2Ring
– PM 2Ring, Commented Apr 30, 2017 at 15:56
Closed, but the link in the close message points to a much too complicated answer. Use this: print(json.dumps(my_json, indent=None, separators=(",",":"))), which results in compact one-line form {"object":{"key":"value","boolean":true},"array":[1,2,3]} — mgaert
– mgaert, Commented Apr 3, 2020 at 8:33
An overeager close in me opinion. It's a very simple question and the close hint points to a very complex answer. mgaert above provided a one-liner that does the trick. — Dariusz
– Dariusz, Commented Jul 31, 2020 at 10:51
what about when the array is 100's or 1000's of items in length? how are you rendering the json string? maybe you can use a different program to render and explore the json like firefox or chrome browers which allow you to expand and collapse the shelves? — skullgoblet1089
– skullgoblet1089, Commented Jul 31, 2020 at 12:00

Harshana · Accepted Answer · 2020-12-25 04:07:52Z

12

Your task can be fulfilled by using a library like jsbeautifier

Install the library by using:

pip install jsbeautifier

Then add the options and call the jsbeautifier.beautify() function.

Full Code:

import json
import jsbeautifier


my_list = [1, 2, 3]
my_dict = {"key": "value", "boolean": True}
my_json = {"object": my_dict, "array": my_list}

options = jsbeautifier.default_options()
options.indent_size = 2
print(jsbeautifier.beautify(json.dumps(my_json), options))

Output:

{
  "object": {
    "key": "value",
    "boolean": true
  },
  "array": [1, 2, 3]
}

answered Dec 25, 2020 at 4:07

Harshana

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3 Comments

felipe Over a year ago

Does the project have a repo? Can't find anything for it...

user18099 Over a year ago

github.com/beautify-web/js-beautify, I think Is linked on the homepage pypi.org/project/jsbeautifier

enoted Over a year ago

awesome repo, it saved me an evening from reinventing a wheel.

Tiago Pitchon · Accepted Answer · 2022-09-16 19:09:31Z

You don't need any new module to solve this problem. The JSON output is a string type and you can use a loop and an if/elif/else to solve it as in the example below:

import json

my_list = [1, 2, 3]
my_dict = {"key": "value", "boolean": True}
my_json = {"object": my_dict, "array": my_list}

json_dumps = json.dumps(my_json, indent=4)

str_to_write = ''
skip = 0
for char in json_dumps :
    if (skip == 1) and ((char == '\n') or (char == ' ')) :
        pass
    elif (char == '[') :
        skip = 1
        str_to_write = str_to_write + char
    elif (char == ']') :
        skip = 0
        str_to_write = str_to_write + char
    else :
        str_to_write = str_to_write + char

print(str_to_write)

Unfortunatly, it also strips the space character inside the lists. The output is:

{
    "object": {
        "key": "value",
        "boolean": true
    },
    "array": [1,2,3]
}

Using regex module, you can keep the spaces:

import regex as re
import json

my_list = [1, 2, 3]
my_dict = {"key": "value", "boolean": True}
my_json = {"object": my_dict, "array": my_list}

json_dumps = json.dumps(my_json, indent=4)

start = [m.start() for m in re.finditer('\[', json_dumps)]
end = [m.start() + 1 for m in re.finditer('\]', json_dumps)]
original = []
alterated = []
for s, e in zip(start, end) :
    original.append(json_dumps[s:e])
    alterated.append(json_dumps[s:e].replace('\n', '').replace('    ', '').replace(',', ', '))
for o, a in zip(original, alterated) :
    json_dumps = json_dumps.replace(o, a)

print(json_dumps)

The output:

{
    "object": {
        "key": "value",
        "boolean": true
    },
    "array": [1, 2, 3]
}

The problem with this method that typically you still want to indent the lists that have nested elements. E.g. list like [ [1,1,3], [1,1,3] ] you want each sublist to be on their own line.

FamousSnake · Accepted Answer · 2025-08-28 13:05:10Z

1

I have a solution but it's hacky and involving monkey patching json's library encoder.py.

import json
a = {
    "header": [["l","f","f"],["f","f","f"]],
    "data": [[1,1,3], [1,1,3]]
}
json.encoder.pretty_json_lists = True
print(json.dumps(a, indent=4))

Resulting in json like so:

{
    "header": [
        ["l","f","f"],
        ["f","f","f"]
    ],
    "data": [
        [1,1,3],
        [1,1,3]
    ]
}

Patched encoder.py can be found here - https://gist.github.com/Andrej730/38febfb059e12f3e67fe72703414ccf9

edited Aug 28 at 13:05

answered Dec 8, 2023 at 18:31

FamousSnake

4696 silver badges14 bronze badges

Comments

Christopher Blodgett · Accepted Answer · 2024-05-31 19:24:12Z

0

Per the python documentation you can just replace the separators.

Compact encoding:

>>>
>>> import json
>>> json.dumps([1, 2, 3, {'4': 5, '6': 7}], separators=(',', ':'))
'[1,2,3,{"4":5,"6":7}]'

answered May 31, 2024 at 19:24

Christopher Blodgett

12 bronze badges

Comments

0xUu · Accepted Answer · 2024-11-21 08:48:55Z

Probably this won't help you much, but you could definitely use Regex (all white considering your context).

Here is code I used in one of my projects.

def pretty_json(data):
    """
    With the power of regex, remove the annoying \n inside an array in `le Jeson`
    Our input (json output) looks like this:
        {
        |    "num_nodes": 8,
        |    "adjacency_matrix": [
        |        [
        |            "",
        |            "H",
        |        ],
        |        [
        |            "E",
        |            0,
        |       ]
        |    ],
        |    "adjacency_list": {
        |    |   "H": [
        |    |       {
        |    |           "node": "F",
        |    |           "weight": 1
        |    |       },
        |    |       {
        |    |           "node": "G",
        |    |           "weight": 1
        |    |       }
        |    |   ],
        |    }
        }
    We'll turn this boi into something more readable
    """

    # define the necessary matches
    SBRACKET = r'\[\n\s+"'
    CBRACKET = r'\{\n\s+'

    C_INSIDE = r'",\n\s+'
    C_INSIDE_LF = r'(")\n\s+\]'

    D_INSIDEARR = r'(\d,)\n\s+'
    D_INSIDEARR_LF = r'(\d)\n\s+\]'
    D_INSIDEOBJ_LF = r'(\d)\n\s+\}'

    # replace all occurrences
    data = re.sub(SBRACKET, '[ "', data)
    data = re.sub(C_INSIDE, '", ', data)
    data = re.sub(D_INSIDEARR, r'\1 ', data)
    data = re.sub(D_INSIDEARR_LF, r'\1 ]', data)
    data = re.sub(C_INSIDE_LF, r'\1 ]', data)
    data = re.sub(CBRACKET, '{ ', data)
    data = re.sub(D_INSIDEOBJ_LF, r'\1 }', data)

    return data

Data generated by it (Not perfect)

{ "num_nodes": 8, "adjacency_matrix": [
        [ "", "S7", "S5", "S3", "S4", "S6", "S8", "S2", "S1" ],
        [ "S7", 0, 0, 0, 1, 1, 1, 0, 0 ],
        [ "S5", 0, 0, 1, 0, 1, 0, 1, 1 ],
        [ "S3", 0, 1, 0, 0, 1, 0, 0, 1 ],
        [ "S4", 1, 0, 0, 0, 1, 0, 1, 0 ],
        [ "S6", 1, 1, 1, 1, 0, 1, 0, 0 ],
        [ "S8", 1, 0, 0, 0, 1, 0, 0, 0 ],
        [ "S2", 0, 1, 0, 1, 0, 0, 0, 1 ],
        [ "S1", 0, 1, 1, 0, 0, 0, 1, 0 ]
    ],
    "adjacency_list": { "S7": [
            { "node": "S8", "weight": 1 },
            { "node": "S4", "weight": 1 },
            { "node": "S6", "weight": 1 }
        ],
        "S5": [
            { "node": "S1", "weight": 1 },
            { "node": "S6", "weight": 1 },
            { "node": "S3", "weight": 1 },
            { "node": "S2", "weight": 1 }
        ],
        "S3": [
            { "node": "S6", "weight": 1 },
            { "node": "S5", "weight": 1 },
            { "node": "S1", "weight": 1 }
        ],
        "S4": [
            { "node": "S7", "weight": 1 },
            { "node": "S6", "weight": 1 },
            { "node": "S2", "weight": 1 }
        ],
        "S6": [
            { "node": "S8", "weight": 1 },
            { "node": "S4", "weight": 1 }
        ],
        "S8": [
            { "node": "S6", "weight": 1 },
            { "node": "S7", "weight": 1 }
        ],
        "S2": [
            { "node": "S1", "weight": 1 },
            { "node": "S5", "weight": 1 }
        ],
        "S1": [
            { "node": "S5", "weight": 1 },
            { "node": "S3", "weight": 1 }
        ]
    }
}

Note that you have to json.dumps() your input first with an indent argument set

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