On Mon, Oct 24, 2011 at 1:04 PM, Johan Martinez <jmart...@gmail.com> wrote:
> Hi, > > I am struggling to understand Python string immutability. I am able to > modify Python string object after initializing/assigning it a value. So how > does immutability work? I am not following it. Sorry for really stupid > question. Any help? > > <code> > > >>> s = "First" > >>> print s.__class__ > <type 'str'> > >>> print s > First > >>> s = "Second" > This is not actually modifying the string object. Unlike most other programming languages where a variable refers to an actual location in memory (usually), in Python the variable names the actual value. So when you do s = "First" then you are telling python that you want to be able to refer to the string "First" by the name/variable s. When you execute s="Second" you are now telling python that instead of referring to "First" you want the name 's' to refer to the string "Second". If you try to modify the actual value of the string, you will raise an exception: >>> s = "First" >>> s[0] = "T" Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'str' object does not support item assignment HTH, Wayne
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