Python Bool and int comparison and indexing on list with boolean values

Question

Indexing on list with boolean values works fine. Though the index should be an integer.

Following is what I tried in console:

>>> l = [1,2,3         


        

Answer 1

What's going on is that booleans actually are integers. True is 1 and False is 0. Bool is a subtype of int.

>>> isinstance(True, int)
True
>>> issubclass(bool, int)
True

So it's not converting them to integers, it's just using them as integers.

(Bools are ints for historical reasons. Before a bool type existed in Python, people used the integer 0 to mean false and 1 to mean true. So when they added a bool type, they made the boolean values integers in order to maintain backward compatibility with old code that used these integer values. See for instance http://www.peterbe.com/plog/bool-is-int .)

>>> help(True)
Help on bool object:

class bool(int)
 |  bool(x) -> bool
 |  
 |  Returns True when the argument x is true, False otherwise.
 |  The builtins True and False are the only two instances of the class bool.
 |  The class bool is a subclass of the class int, and cannot be subclassed.