When is self statement true and when is false?

Question

Can someone explain this if self.cards condition? When will it be True and when will it be False?

def __init__(self):
    self.cards = []

def __str__(self):
    if self.cards:
        rep = ""
        for card in self.cards:
            rep += str(card) + " "
    else:
        rep = "<empty>"
    return rep

Answer 1

Any object can be tested for truth value in Python. The following values are considered false:

None

False

zero of any numeric type, for example, 0, 0L, 0.0, 0j.

any empty sequence, for example, '', (), [].

any empty mapping, for example, {}.

instances of user-defined classes, if the class defines a __nonzero__() or __len__() method, when that method returns the integer zero or bool value False.

All other values are considered true — so objects of many types are always true.

In this case cards is False when it is empty because it is a list. When the object is created, __init__() creates the cards empty list, so that if statement's condition is always False when the object is created.