I only changed self._hiddenlist into self when formatting; it'll output a recursion error. What does it actually mean and why?

Question

class Queue:
def __init__(self, contents):
self._hiddenlist = list(contents)

def push(self, value):
self._hiddenlist.insert(0, value)

def pop(self):
return self._hiddenlist.pop(-1)

def __repr__(self):
return "Queue({})".format(self)

queue = Queue([1, 2, 3])
print(queue)
queue.push(0)
print(queue)
queue.pop()
print(queue)
print(queue._hiddenlist)

Answer 1

It gives a recursion error because when you use a non-string object as a format parameter, Python will automatically call __repr__ on the object. The thing is, in your __repr__, Python keeps having to call __repr__ to get the string representation until the recursion depth limit is reached.

EDIT: Essentially, the __repr__() definition boils down to:
return "Queue({})".format("Queue({})".format("Queue({})".format("Queue({})"...

Answer 2

LunarCoffee you're saying if there's no __str__ magic method added python calls the repr function (which is called when the object as an arg in the print function) to get the string representation. Is that right?

Answer 3

In your __repr__() function you put self as the parameter for format(), instead of self._hiddenlist.

Answer 4

yash
When __repr__() is defined but __str__() is not, Python behaves as if __str__ = __repr__.

Answer 5

Yes, I'm aware of that😅
I was changing up stuff to test things out
I was asking: what does it even mean if I am to do this?

Answer 6

Awesome. Thanks guys💪

Answer 7

So __repr__() can take the place of __str__() if there's not one?
What else can it take the place of?