Python 'is' vs JavaScript ===

Question

The Python use of \'is\' seems to be similar to JavaScript \'===\' but not quite.

Here they talk about exact instances: http://www.learnpython.org/en/Conditions

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Answer 1

>>> a = "Hello, World!!!"
>>> b = "Hello, World!!!"
>>> a is b
False

However note that:

>>> a = "Bob"
>>> b = "Bob"
>>> a is b
True

In this case it condition was True because the compiler is free to intern string literals, and thus reuse the same object, and it does do that with small strings. However there is no guarantee as to when this happens of if this happens at all and the behaviour changes between versions and implementations.

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A realiable False output should be:

>>> a = 'Hello, World!!!!'[:-1]
>>> b = 'Hello, World!!!!'[:-1]
>>> a is b
False

Or anything that actually computes the strings.