I can't understand why it won't return True always, since the ''return True&#039-CodePudding

Assuming played_chicket and winning_chicket are 2 random lists wiht 4 elements each, what does this loop returns? I can't understand the logic behind it. Won't it return True always because the ''return True'' statement is outside the loop? I know it will return false if any of the elements are different but i can't see why. Can someone please, explain it to me?

def check_ticket(played_ticket, winning_ticket):
    # Check all elements in the played ticket. If any are not in the 
    #   winning ticket, return False.
    for element in played_ticket:
        if element not in winning_ticket:
            return False
     
    # We must have a winning ticket!
    return True

CodePudding user response：

This is most likely because the first element in played_ticket is not in winning_ticket

Consider played_ticket = [0,1,2] and winning_ticket = [1,2]

Your first iteration will look like this:

    for element in played_ticket:
        # element = 0
        if element not in winning_ticket:
            # 0 is not in winning_ticket, so it will return false immediately
            return False

Your function as is will always return False or nothing (becomes None). You will need to edit the function to have a fallback return True:

def check_ticket(played_ticket, winning_ticket):
    # Check all elements in the played ticket. If any are not in the
    #   winning ticket, return False.
    for element in played_ticket:
        if element not in winning_ticket:
            return False
    # Here
    return True

So if every element is in the other list, it will return True

See this discussion if you would like to simplify your function

CodePudding user response：

by turning winning ticket into a list you could invert the process checking if the element is True, return False if nothing is True:

def check_ticket(played_ticket, winning_ticket):
# Check all elements in the played ticket. If any are not in the 
#   winning ticket, return False.
    if any(element in winning_ticket for element in played_ticket):
        return True
    return False