Write Past Value in data.txt - python-3.x

Question

I want to write some list in data.txt.
The output from program is:
Triangle
('(a1, b1)', '(a2, b2)', '(a3, b3)')
Triangle
('(a4, b4)', '(a5, b5)', '(a6, b6)')
With this lines of code to write in data.txt;
data = {}
data['shapes'] = []
data['shapes'].append({
'name': str(triangle.name),
'Vertices': list(triangle.get_points())
I need output in my data.txt with json format like this:
{"shapes": [{"name": "Triangle", "Vertices": ["(a1, b1)", "(a2, b2)", "(a3, b3)"]}, {"name": "Triangle", "Vertices": ["(a4, b4)", "(a5, b5)", "(a6, b6)"]}]}
But this is what I get:
{"shapes": [{"name": "Triangle", "Vertices": ["(a4, b4)", "(a5, b5)", "(a6, b6)"]}]}
So, how can I write the past value of triangle that have vertices (a1, b1)...(a3, b3)?

Answer 1

This part of your code should be executed only once:
data = {}
data['shapes'] = []
The following part of your code you should execute repeatedly
data['shapes'].append({
'name': str(triangle.name),
'Vertices': list(triangle.get_points())
probably in a loop similar to this one
for triangle in triangles:
data['shapes'].append({
'name': str(triangle.name),
'Vertices': list(triangle.get_points())

Answer 2

It seems like you're overwriting the variable referencing the first triangle object with the next triangle object before appending the first triangle object's information to data['shapes'].
That block of code where you append to your data['shapes'] should be executed twice, once for each triangle object.