如何从 python 中的 object 创建正确的 JSON？

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!

Answer 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.