对参数key使用lambda切割字符串，然后int转化数值进行排序，代码如下：

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a = ['gene1', 'gene100', 'gene2', 'gene3', 'gene300']
a.sort(key=lambda x: int(x.split('gene')[1]))
print a
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['gene1', 'gene2', 'gene3', 'gene100', 'gene300']

sorted()函数同理