Python编程 从入门到实践 第3章 列表简介

1 在Python中，用方括号 [ ] 来表示列表

bicycles = ['trek','cannondale','redline']

python支持不同类型元素在同个列表中

>>> a = [1,1.0,'11']
>>> a
[1, 1.0, '11']

2 列表的修改，添加和删除

• 访问列表，可以用索引，从0开始。指定某个索引进行修改

>>> motorcycles = ['honda','yamaha','suzuki']
>>> motorcycles
['honda', 'yamaha', 'suzuki']
>>> motorcycles[0] = 'ducati'
>>> print(motorcycles)
['ducati', 'yamaha', 'suzuki']

• 添加元素，用append() 在列表末尾添加。用insert()在列表任何位置添加

>>> motorcycles.append('hello')
>>> print(motorcycles)
['ducati', 'yamaha', 'suzuki', 'hello']
>>> motorcycles.insert(0,'first')
>>> print(motorcycles)
['first', 'ducati', 'yamaha', 'suzuki', 'hello']
>>> motorcycles.insert(3,'third')
>>> print(motorcycles)
['first', 'ducati', 'yamaha', 'third', 'suzuki', 'hello']

• 删除元素，用del 语句

>>> print(motorcycles)
['first', 'ducati', 'yamaha', 'third', 'suzuki', 'hello']
>>> del motorcycles[0]    # 删除第一个元素
>>> print(motorcycles)
['ducati', 'yamaha', 'third', 'suzuki', 'hello']

• 删除元素，也可用pop()函数

>>> print(motorcycles)
['ducati', 'yamaha', 'third', 'suzuki', 'hello']
>>> a = motorcycles.pop()   #删除倒数第一个
>>> print(motorcycles)
['ducati', 'yamaha', 'third', 'suzuki']
>>> a
'hello'
>>> a = motorcycles.pop(-2)   #删除倒数第二个
>>> print(motorcycles)
['ducati', 'yamaha', 'suzuki']
>>> a
'third'
>>> a = motorcycles.pop(0)   #删除第一个
>>> print(motorcycles)
['yamaha', 'suzuki']
>>> a
'ducati'

• 删除元素，也可用remove()根据值删除。remove() 函数只删除掉检索的第一个指定值。

>>> print(motorcycles)
['yamaha', 'suzuki']
>>> motorcycles.remove('suzuki')
>>> print(motorcycles)
['yamaha']

3 sort() 函数对列表排序，默认升序。如果想倒序，可以传递参数reverse=True

>>> cars = ['bmw','audi','toyota','subaru']
>>> cars.sort()
>>> cars
['audi', 'bmw', 'subaru', 'toyota']
>>> cars.sort(reverse=True)  #倒序
>>> cars
['toyota', 'subaru', 'bmw', 'audi']

4 sorted()函数对列表排序，但不改变原列表

>>> print(sorted(cars))
['audi', 'bmw', 'subaru', 'toyota']
>>> cars
['toyota', 'subaru', 'bmw', 'audi']

5 倒着打印列表，用reverse()

>>> cars = ['bmw','audi','toyota','subaru']
>>> print(cars)
['bmw', 'audi', 'toyota', 'subaru']
>>> cars.reverse()
>>> print(cars)
['subaru', 'toyota', 'audi', 'bmw']

6 用len()函数确定列表的长度

>>> cars = ['bmw','audi','toyota','subaru']
>>> len(cars)
4

7 列表的索引，从0开始，0表示第一个，-1表示倒数第一个，-2表示倒数第二个。