aren't python strings immutable?
<p>My understanding was that python strings are immutable. </p>

<p>I tried the following code:</p>

<pre><code>a = "Dog" 
b = "eats"
c = "treats"

print a  , b , c
# Dogeatstreats
print a + " " + b + " " + c
#Dog eats  treats
print a
#Dog
a = a +  " " + b + " " + c

print a
#Dog eats  treats
#!!!
</code></pre>

<p>Shouldn't python prevented the assignment? I am probably missing something.</p>

<p>Any idea?</p>
