 <p>You can copy the original list by slicing it:</p> <pre><code>a = [1, 2, 3] b = a[:] </code></pre> <p>Or using the built in list list() funtion:</p> <pre><code>b = list(a) </code></pre> <p>You could also use list comprehension in place of your nested for loops:</p> <pre><code>b = [[i if i else 1 for i in j] for j in a] </code></pre>