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copied!<p>In python, if you're doing this with non-primitive types, it acts exactly like you want: assigning is done using references. That's why, when you run the following:</p> <pre><code>>>> a = {'key' : 'value'} >>> b = a >>> b['key'] = 'new-value' >>> print a['key'] </code></pre> <p>you get <code>'new-value'</code>. Strictly saying, if you do the following:</p> <pre><code>>>> a = 5 >>> b = a >>> print id(a) == id(b) </code></pre> <p>you'll get True.</p> <p><strong>But!</strong> Because of primitive types are immutable, you cant change the value of variable <code>b</code> itself. You are just able create a new variable with a new value, based on <code>b</code>. For example, if you do the following:</p> <pre><code>>>> print id(b) >>> b = b + 1 >>> print id(b) </code></pre> <p>you'll get two different values.</p> <p>This means that Python created a new variable, computed its value basing on b's value and then gave this new variable the name <code>b</code>. This concerns all of the immutable types. Connecting two previous examples together:</p> <pre><code>>>> a = 5 >>> b = a >>> print id(a)==id(b) True >>> b += 1 >>> print id(b)==id(a) False </code></pre> <p>So, when you assign in Python, you always assign reference. But some types cannot be changed, so when you do some changes, you actually create a new variable with another reference.</p>

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