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python list generator

高洛峰
高洛峰Original
2016-11-19 15:51:151261browse

In actual situations, we often need to generate some lists. In addition to the relatively inefficient use of a for loop to append to the list one by one, is there any better way?
Python provides us with a very powerful way to create lists.

For example, we need to create a data list from 1 to 100.

range(1,101)

We want to create a list of 12,22,32...1002, how can we achieve it?

[x*x for x in range(1,101)]
  |     |------------------ x取得1,2,3,4....100列表
  |------------------------- 对列表中的元素进行平方计算

How do we first judge whether the list is what we need? We can use if.

[x*x for x in range(1,1001) if x%2==0]
                                  |------先对x进行判断,是偶数的则留下

Multiple Loop Survival Full Permutation List For example, if we need to generate all 9*9 multiplication tables, then we can use double loop.

[str(x)+"*"+str(y)+"="+str(x*y) for x in range(0,10) for y in range(0,10)]

In the above code, the outer loop is x and the inner loop is y.

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