I am learning python by implementing a website with fastApi ; I have many years of experience in C#. I have this code :

testModule.py :

class testClass:    
    async def test(self):
        r = DataSet()
        for i in range(0, 10):
            r.Tables.append(Table())
            r.Tables[i].Rows.append(dict[int, int]())
            r.Tables[i].Rows[0][0] = 0

Dataset.py:

class Table:
    Rows: list[dict[str, Any]] = []


class DataSet:
    Tables: list[Table] = []

testModule.py :

class testClass:    
    async def test(self):
        r = DataSet()
        for i in range(0, 10):
            r.Tables.append(Table())
            r.Tables[i].Rows.append(dict[int, int]())
            r.Tables[i].Rows[0][0] = 0

main.py :

@app.get("/test")

async def test(instance: Annotated[testClass, Depends()]):
    res = await instance.test()

    return res

When I call the test route and I set a breakpoint on the line r.Tables[i].Rows[0][0] = 0, at the second loop, my debugger shows me this :

Why the second Table instance already contains items, even if I didn’t add any yet ?