Python列表生成器的循环技巧分享
列表生成式即List Comprehensions，是Python内置的非常简单却强大的可以用来创建list的生成式。
一个循环
在C语言等其他语言中，for循环一般是这样的
如果python也这么写，那么真该看下python的基础教程了~
但要注意的是，需要加一个[]来，否则会报错...
在上面的例子中，不仅可以嵌套for，甚至可以嵌套if语句
再看看，原来是什么样子
两个循环呢？
原来可能是这样的？
现在可以这样了！！！
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