Why does 1 == True but 2 != True in Python? [duplicate]

Question

Possible Duplicate:
Is False == 0 and True == 1 in Python an implementation detail or is it guaranteed by the language?

A brief transcript from my interactive console:

Python 2.7.2 (default, Jun 29 2011, 11:10:00)  [GCC 4.6.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> True True >>> 0 == True False >>> 1 == True True >>> 2 == True False 

Why on earth is this the case?

Edit: For the sake of contrast, consider the is operator.

>>> 0 is False False >>> 1 is True False >>> 0 is 0 True >>> True is True True 

That makes a lot of sense because though 1 and True both mean the same thing as the condition of an if statement, they really aren't the same thing.

Edit again: More fun consequences of 1 == True:

>>> d = {} >>> d[True] = "hello" >>> d[1] "hello" 

Answer 1

Because Boolean in Python is a subtype of integers. From the documentation:

Boolean values are the two constant objects False and True. They are used to represent truth values (although other values can also be considered false or true). In numeric contexts (for example when used as the argument to an arithmetic operator), they behave like the integers 0 and 1, respectively. The built-in function bool() can be used to cast any value to a Boolean, if the value can be interpreted as a truth value (see section Truth Value Testing above).

http://docs.python.org/library/stdtypes.html#boolean-values

Answer 2

Because instances of bool are also instances of int in python. True happens to be equals to integer 1.

Take a look at this example:

[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> isinstance(True, int) True >>> int(True) 1 >>>