Ron Adam wrote:
> George Sakkis wrote:
>
>> I get:
>>
>> None: 0.549999952316
>> String: 0.498000144958
>> is None: 0.450000047684
>
>
> What do yo get for "name is 'string'" expressions?
>>> 'abc' is 'abcd'[:3]
False
You need to test for equality (==), not identity (is) when
equal things may be distinct. This is true for floats, strings,
and most things which are not identity-based (None, basic classes).
This is also true for longs and most ints (an optimization that makes
"small" ints use a single identity can lead you to a mistaken belief
that equal integers are always identical.
>>> (12345 + 45678) is (12345 + 45678)
False
'is' tests for identity match. "a is b" is roughly equivalent to
"id(a) == id(b)". In fact an optimization inside string comparisons
is the C equivalent of "return (id(a) == id(b) of len(a) == len(b)
and <elements match>)
--Scott David Daniels
[EMAIL PROTECTED]
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