Python可以分辨一堆不同的复合数据类型,并可以将他们整合在一起。列表(list)就是一种非常出色的方法。它可以用方括号将将一堆以逗号分隔的项整合在一起。可以包含不同的数据类型,但日常使用时常用相同的数据类型。
>>> squares = [1, 4, 9, 16, 25] >>> squares [1, 4, 9, 16, 25]
跟所有的内置序列类型一样(built-in sequence type),对list可以执行索引(index)和切片(slice)操作
>>> squares[0] # indexing returns the item 1 >>> squares[-1] 25 >>> squares[-3:] # slicing returns a new list [9, 16, 25]
所有的slice操作都将返回一个操作后的新list。list也支持像串接( concatenation)的操作
>>> squares + [36, 49, 64, 81, 100] [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
list不像string,它是可变的(mutable),可以改变其中的内容
>>> cubes = [1, 8, 27, 65, 125] # something‘s wrong here >>> 4**3 # the cube of 4 is 64, not 65! 64 >>> cubes[3] = 64 # replace the wrong value >>> cubes [1, 8, 27, 64, 125]
你也可以使用append()方法在list的末尾添加新的项
>>> cubes.append(216) # add the cube of 6 >>> cubes.append(7**3) # and the cube of 7 >>> cubes [1, 8, 27, 64, 125, 216, 343]
使用slice方法对list进行操作时,可以改变list的大小甚至清空
>>> letters = [‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘] >>> letters [‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘] >>> # replace some values >>> letters[2:5] = [‘C‘, ‘D‘, ‘E‘] >>> letters [‘a‘, ‘b‘, ‘C‘, ‘D‘, ‘E‘, ‘f‘, ‘g‘] >>> # now remove them >>> letters[2:5] = [] >>> letters [‘a‘, ‘b‘, ‘f‘, ‘g‘] >>> # clear the list by replacing all the elements with an empty list >>> letters[:] = [] >>> letters []
内置函数len()也同样适用于list
>>> letters = [‘a‘, ‘b‘, ‘c‘, ‘d‘] >>> len(letters) 4
将list作为项整合为list也是可行的
>>> a = [‘a‘, ‘b‘, ‘c‘] >>> n = [1, 2, 3] >>> x = [a, n] >>> x [[‘a‘, ‘b‘, ‘c‘], [1, 2, 3]] >>> x[0] [‘a‘, ‘b‘, ‘c‘] >>> x[0][1] ‘b‘
时间: 2024-10-08 08:16:08