Why is python constructor receiving wrong default value?

Question

I have created a class Queue with a constructor that takes a list as an argument with an empty list as default. Though object q3 is created using no arguments, the default value going inside the constructor is of object q2.

I am using Python 3.8.5 on Ubuntu 20.04 LTS Virtual machine.

class Queue:
    def __init__(self,elements = []):
        self.elements = elements
        print(elements)
    
    def enqueue(self,element):
        self.elements.append(element)

    def dequeue(self):
        return self.elements.pop(0)

    def peek(self):
        if len(self.elements)>0:
            return self.elements[0]
        else:
            return None


q1 = Queue(["Q1_abc","Q1_def","Q1_ghi"])
q2 = Queue()

q2.enqueue("Q2_abc")
q2.enqueue("Q2_def")
q2.enqueue("Q2_ghi")

q3 = Queue()
q3.enqueue("Q3_abc")
print(q3.elements)

q3 = Queue()
q3.enqueue("Q3_abc")
print(q3.elements)

Output:
['Q1_abc', 'Q1_def', 'Q1_ghi']
[]
['Q2_abc', 'Q2_def', 'Q2_ghi']
['Q2_abc', 'Q2_def', 'Q2_ghi', 'Q3_abc']