How to create correct JSON from an object in python?

Question

I created an object looks like this:

class Rectangle:
    def __init__(self, ymin, xmin, ymax, xmax):
        self.y_min = ymin
        self.x_min = xmin
        self.y_max = ymax
        self.x_max = xmax

    def tojson(self):
        return json.dumps(self, default=lambda o: o.__dict__,
                          sort_keys=False, indent=4)

I have a more complex object but it is enought to explain. If a create a new Rectangle and call tojson() I get the object in the format I need.

rect1 = Rect(1,2,3,4)
print(rect.tojson())

result:

{
    "y_min": 1,
    "x_min": 2,
    "y_max": 3,
    "x_max": 4
}

But if I have Rectangle list and I want to create a JSON, I get them in one row.

rects = [rect1, rect2]
print(json.dumps(rects, default = lambda x: x.__dict__))

result:
[{"y_min": 1, "x_min": 2, "y_max": 3, "x_max": 4}, {"y_min": 1, "x_min": 2, "y_max": 3, "x_max": 4}]

Could you please help me, how could I do this properly? Thank you in advance for your help!

What is your issue? Is it just the json formating? the json generated for the list is good for a json synatx point of view? — Jean-Marc Volle
– Jean-Marc Volle, Commented Apr 30, 2020 at 11:34
Try print(json.dumps(rects, default = lambda x: x.__dict__), indent=4) — martineau
– martineau, Commented Apr 30, 2020 at 11:42

Mies van der Lippe · Accepted Answer · 2020-04-30 11:41:08Z

1

You can use the indent and sort_keys values:

print(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4))

https://docs.python.org/3/library/json.html

You're already doing that in your first example but not in your second.

edited Apr 30, 2020 at 11:41

answered Apr 30, 2020 at 11:35

Mies van der Lippe

7121 gold badge5 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

THE_GREAT_MARKER Over a year ago

Thank you! I used it in the object, but forgot using in case of list. :) Helped me a lot!

Collectives™ on Stack Overflow

How to create correct JSON from an object in python?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related