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POpython sort list of lists with casting
 

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    <p>I know tat similar questions has been asked already several times. And i do now how to use the search function, but it still does not work. </p> <p>So here is the problem setup. I have a list of lists containing strings. One column contains strings which actually represent float values. And it is also the column i want to sort by. The problem is, that python seems to ignore the - (minus) sign on entries. So an example list of: </p> <pre><code>[[blaa, '0.3', bli], [bla, '0.1', blub], [bla, '-0.2', blub]] </code></pre> <p>gets sorted like this:</p> <pre><code>[[bla, '0.1', blub], [bla, '-0.2', blub], [blaa, '0.3', bli]] </code></pre> <p>and not how it should be:</p> <pre><code>[[bla, '-0.2', blub],[bla, '0.1', blub], [blaa, '0.3', bli]] </code></pre> <p>So far i have tried:</p> <ul> <li>casting the second column to float and sorting by that column</li> </ul> <p>like:</p> <pre><code>for i in mylist: i[1] = float(i[1]) mylist.sort(key=lambda x: x[1]) </code></pre> <p>or with</p> <pre><code>for i in mylist: i[1] = float(i[1]) mylist.sort(key=operator.itemgetter(1)) </code></pre> <ul> <li>I also tried to define my own compare function:</li> </ul> <p>like:</p> <pre><code>mylist.sort(cmp=lambda x,y: cmp(float(x), float(y)), key=operator.itemgetter(1)) </code></pre> <p>And any other combination of the above methods, also the same with <code>sorted</code>. So far with no success, the minus sign gets ignored every time. How do is solve this? </p> <p><strong>[edit]</strong> Also already tried the Ignacio suggestion. I should mention i HAVE to use python 2.5 .</p>
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    1. COSo that might be the environmental issues. Check your python version.
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      1. USKabie
    2. COIf you mean for something to be strings, you should really put quotes around it as a consideration to people that might want to run your code.
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    3. COHow certain are you that they're all strings?
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      1. USIgnacio Vazquez-Abrams
 

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