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<qhelp>

<overview>

<p>If you concatenate strings in a loop then the time taken by the loop is quadratic in the number

of iterations.</p>

</overview>

<recommendation>

<p>Initialize an empty list before the start of the loop.

During the loop append the substrings to the list.

At the end of the loop, convert the list to a string by using <code>''.join(list)</code>.</p>

</recommendation>

<references>

<li>Python Standard Library: <a href="http://docs.python.org/library/string.html#string.join">The str.join method</a>.</li>

<li>Python Frequently Asked Questions: <a href="http://docs.python.org/3/faq/programming.html#what-is-the-most-efficient-way-to-concatenate-many-strings-together">

What is the most efficient way to concatenate many strings together?</a>.</li>

</references>

</qhelp>