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

Python used to lack booleans, we just used integers, 0 for False and any other integer for True. So when booleans were added to the language, the values False and True, can be treated as the integer values 0 and 1 still by the interpreter, to help backwards compatibility. Internally, bool is a sub-class of int.

In other words, the following equations are True:

>>> False == 0
True
>>> True == 1
True
>>> isinstance(True, int)
True
>>> issubclass(bool, int)
True

and as you found out:

>>> True * 3
3

This doesn't extend to strings however.

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.