Instead of a list with some objects in it, I get [...] whenever I run my code. I'd like to know what it means, in order to debug my code.
That most probably is a reference to the object itself. Example:
In [1]: l = [0, 1]
In [2]: l.append(l)
In [3]: l
Out[3]: [0, 1, [...]]
In the above, the list l contains a reference to itself. This means, you can endlessly print elements within it (imagine [0, 1, [0, 1, [0, 1, [...]]]] and so on) which is restricted using the ... IMO, you are incorrectly appending values somewhere in your code which is causing this.
A more succinct example:
In [1]: l = []
In [2]: l.append(l)
In [3]: l
Out[3]: [[...]]