How naive is Python?
duncan.booth at invalid.invalid
Mon Jan 15 09:47:22 CET 2007
Roy Smith <roy at panix.com> wrote:
> All of those just move around pointers to the same (interned) string.
Correct about the pointers, but the string is not interned:
Steven D'Aprano <steve at REMOVEME.cybersource.com.au> wrote:
>>>> s1 = foo()
>>>> s2 = foo()
>>>> s1 == s2, s1 is s2
> (True, True)
> So the string "This is a test" within foo is not copied each time the
> function is called. However, the string "This is a test" is duplicated
> between foo and foo2 (the two functions don't share the same string
>>>> s3 = foo2()
>>>> s3 == s1, s3 is s1
> (True, False)
In this specific example the two functions don't share the same string, but
that won't always be the case: if the string had been interned this would
have printed (True, True).
e.g. Removing all the spaces from the string produces a string which is
>>> def foo():
s = "Thisisatest"
>>> def foo2():
>>> s1 = foo()
>>> s2 = foo2()
>>> s1 is s2
Bottom line, never make assumptions about when two literal strings will
share the same object and when they won't.
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