from timeit import Timer def test(): li=[] for i in range(10000): li.append(i) def test2(): li=[i for i in range(10000)] t=Timer("test()","from __main__ import test") print("for循环生成list:",t.timeit(1000)) t2=Timer("test2(
一般Python for语句前不加语句,但我在机器学习实战中看到了这两条语句: featList = [example[i] for example in dataSet] classList = [example[-1] for example in dataSet] 多方研究和询问,得到如下解释: 语句featList = [example[i] for example in dataSet]作用为: 将dataSet中的数据按行依次放入example中,然后取得example中的examp
# For More :http://www.codebelief.com/article/2017/02/python-advanced-programming-list-comprehensions/ # 列表生成可以非常方便地用来生成列表和迭代器 # 比如上节中map的两个例子和filter的一个例子可以用列表生成重写为 [x**2 for x in [1, 2, 3, 4]] # [1, 4, 9 16] [sum(x) for x in zip([1, 2, 3], [5, 6, 7]