On 2011-10-24 20:04, Johan Martinez wrote:
Hi,
I am struggling to understand Python string immutability. I am able to
modify Python string object after initializing/assigning it a value.
s = "First"
print s.__class__
<type 'str'>
print s
First
s = "Second"
print s
Second
Dave, Sander and Wayne have already explained why you aren't modifying
string objects in your example.
With the id()-function you can also see what is happening:
>>> s = "First"
>>> id(s)
3077110080L # In CPython this is the memory address of the object
# with the name 's' (in your case "First")
>>> s = "Second"
>>> id(s)
3077110304L # You see that 's' refers now to another address
>>> id("First")
3077110080L # But "First" is still on the same address as before
>>> id("Second")
3077110304L # And this proves that "Second" is at the address
# which 's' refers to
Bye, Andreas
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