Why are mutable strings slower than immutable strings?
<p>Why are mutable strings slower than immutable strings?</p>

<p>EDIT:</p>

<pre><code>&gt;&gt;&gt; import UserString
... def test():
...     s = UserString.MutableString('Python')
...     for i in range(3):
...         s[0] = 'a'
... 
... if __name__=='__main__':
...     from timeit import Timer
...     t = Timer("test()", "from __main__ import test")
...     print t.timeit()
13.5236170292



&gt;&gt;&gt; import UserString
... def test():
...     s = UserString.MutableString('Python')
...     s = 'abcd'
...     for i in range(3):
...         s = 'a' + s[1:]
... 
... if __name__=='__main__':
...     from timeit import Timer
...     t = Timer("test()", "from __main__ import test")
...     print t.timeit()
6.24725079536


&gt;&gt;&gt; import UserString
... def test():
...     s = UserString.MutableString('Python')
...     for i in range(3):
...         s = 'a' + s[1:]
... 
... if __name__=='__main__':
...     from timeit import Timer
...     t = Timer("test()", "from __main__ import test")
...     print t.timeit()
38.6385951042
</code></pre>

<p>i think it is obvious why i put s = UserString.MutableString('Python') on second test.</p>

<p>NOTE: downvotes with no sense, and no comments i will report those downvoters.</p>
