String Methods Don't Change ID?

[Peter Hansen]

Kamilche wrote:
> 
> I am reading a book on Python, 'Core Python Programming.' They have
> hammered home how when you change a string, or reassign it, the ID
> changes.
> 
> But now, I'm looking the following example, which modifies a string,
> but the ID doesn't change. Can anyone explain why the built-in string
> methods don't modify the ID?

You forgot to prove that the example modifies the string:

> >>> quest = 'what is your favorite color?'
> >>> id(quest)
> 10988760
> >>> quest.capitalize()
> 'What is your favorite color?'
> >>> id(quest)
> 10988760
> >>> quest.center(40)
> '      what is your favorite color?      '
> >>> id(quest)
> 10988760
> >>>

Finish up your example by typing "quest" again:

>>> quest
'what is your favorite color?'

Hmm.... neither very centered, nor capitalized, is it?  So it hasn't 
been modified. ;-)

I like Brett's answer: "strings are immutable (keep repeating that)".

-Peter