Question

I’m implementing some basic data structures in preparation for an exam and have come across the following issue. I want to implement an unsorted linked list, and have already implemented a pop() method, however I don’t know, either syntactically or conceptually, how to make a function sometimes take an argument, sometimes not take an argument. I hope that makes sense.

def pop(self):
    current = self.head
    found = False
    endOfList = None

    while current != None and not found:
        if current.getNext() == None:
            found = True
            endOfList = current.getData()
            self.remove(endOfList)
            self.count = self.count - 1
        else:
            current = current.getNext()

    return endOfList

I want to know how to make the statement unsortedList.pop(3) valid, 3 being just an example and unsortedList being a new instance of the class.

Answer 1

The basic syntax (and a common use case) for using a parameter with a default value looks like this:

def pop(self, index=None):
    if index is not None:
        #Do whatever your default behaviour should be

You then just have to identify how you want your behaviour to change based on the argument. I am just guessing that the argument should specify the index of the element that should be pop’ed from the list.

If that is the case you can directly use a valid default value instead of None e.g. 0

def pop(self, index=0):