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POSwap first and last letter of a string in Python
 

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    <p>I hope I'm missing something obvious here, but I was playing around with the Python CodingBat site, and got to the problem <a href="http://codingbat.com/prob/p153599" rel="nofollow">front_back</a>:</p> <blockquote> <p>For a string passed in, return it with its first and last characters swapped, if the string length is greater than 1.</p> </blockquote> <p>I came up with a single line solution which I thought would suffice but Coding.bat refuses to accept it, with an Index out of range error.</p> <p>I've played around in IDLE (64bit windows version) and I've boiled the problem down to this:</p> <pre><code>len(str) &lt; 2 and str or 'doh ' + str + ' /doh' </code></pre> <p>The wierd problem is that setting <code>str = ''</code> returns:</p> <pre><code>'doh /doh' </code></pre> <p>Which it shouldn't as len('') is 0, but <code>str='a'</code> returns:</p> <pre><code>'a' </code></pre> <p>and <code>str='abc'</code> returns:</p> <pre><code>'doh abc /doh' </code></pre> <p>Which I would expect...</p> <p>So my question is really; Why is checking the len of '' going to the OR condition of the ternary operator, but running <code>len('')</code> at the console return 0, which is obviously less than 2?</p> <p><strong>Edit:</strong></p> <p>This solution actually works, however:</p> <pre><code> def front_back(str): if len(str) &lt; 2: return str else: return str[-1] + str[1:-1] + str[0] </code></pre> <p>To 'mtadd'; thanks for your answer but this isn't a logical and/or this is a pythonic ternary operator:</p> <pre><code>return (statement) and &lt;statement was true&gt; or &lt;statement was false&gt; </code></pre> <p>It's the same as C#'s:</p> <pre><code>return statement ? trueValue : falseValue; </code></pre>
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