1.3 List(列表)

列表由一系列按特定顺序排列的元素组成。

在Python中，用方括号[ ]来表示列表，并用逗号来分隔其中的元素。

1.3.1 访问列表元素

在Python中，第一个列表元素的索引为0，而不是1。

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

>>> print(bicycles[0])

trek

>>> print(bicycles[3])

specialized

>>> print(bicycles[-1])

specialized

注意：通过将索引指定为-1，可让Python返回最后一个列表元素。索引-2返回倒数第二个列表元素，索引-3返回倒数第三个列表元素，以此类推。

1.3.2 添加元素

>>> motorcycles = ['honda', 'yamaha', 'suzuki']

>>> print(motorcycles)

['honda', 'yamaha', 'suzuki']

>>> motorcycles.append('ducati')

>>> print(motorcycles)

['honda', 'yamaha', 'suzuki', 'ducati']

1.3.3 修改元素

>>> motorcycles = ['honda', 'yamaha', 'suzuki']

>>> print(motorcycles)

['honda', 'yamaha', 'suzuki']

>>> motorcycles[0] = 'ducati'

>>> print(motorcycles)

['ducati', 'yamaha', 'suzuki']

1.3.4 在列表中插入元素

>>> motorcycles = ['honda', 'yamaha', 'suzuki']

>>> motorcycles.insert(1, 'ducati')

>>> print(motorcycles)

['honda', 'ducati', 'yamaha', 'suzuki']

1.3.5 删除元素

>>> motorcycles = ['honda', 'yamaha', 'suzuki']

>>> print(motorcycles)

['honda', 'yamaha', 'suzuki']

>>> del motorcycles[1]

>>> print(motorcycles)

['honda', 'suzuki']

弹出列表元素

>>> motorcycles = ['honda', 'yamaha', 'suzuki']

>>> popped_motorcycle = motorcycles.pop()

>>> print(popped_motorcycle)

suzuki

>>> print(motorcycles)

['honda', 'yamaha']

>>> print(motorcycles.pop(0))

honda

>>> print(motorcycles)

['yamaha']

有时候，你不知道要从列表中删除的值所处的位置。如果你只知道要删除的元素的值，可使用方法remove()。

>>> motorcycles = ['honda', 'yamaha', 'suzuki']

>>> print(motorcycles)

['honda', 'yamaha', 'suzuki']

>>> motorcycles.remove('yamaha')

>>> print(motorcycles)

['honda', 'suzuki']

1.3.6 对列表排序

>>> cars = ['bmw', 'audi', 'toyota', 'subaru']

>>> cars.sort()

>>> print(cars)

['audi', 'bmw', 'subaru', 'toyota']

>>> print(len(cars))

4

1.3.7 遍历列表

>>> magicians = ['alice', 'david', 'carolina']

>>> for magician in magicians:

print(magician)

alice

david

carolina

>>>

1.3.8 创建数值列表

>>> for value in range(1,5):

print(value)

1

2

3

4

>>>

>>> numbers = list(range(1,6))

>>> print(numbers)

[1, 2, 3, 4, 5]

>>> even_numbers = list(range(2,11,2))

>>> print(even_numbers)

[2, 4, 6, 8, 10]

对数字列表执行简单的统计计算

>>> digits = [1,2,3,4,5,6,7,8,9,0]

>>> min(digits)

0

>>> max(digits)

9

>>> sum(digits)

45

1.3.9 列表生成式(List Comprehensions)

>>> squares = [value**2 for value in range(1,11)]

>>> print(squares)

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

>>> [x * x for x in range(1, 11) if x % 2 == 0]

[4, 16, 36, 64, 100]

>>> [m + n for m in 'ABC' for n in 'XYZ']

['AX', 'AY', 'AZ', 'BX', 'BY', 'BZ', 'CX', 'CY', 'CZ']

>>> d = {'x': 'A', 'y': 'B', 'z': 'C' }

>>> [k + '=' + v for k, v in d.items()]

['x=A', 'y=B', 'z=C']

>>> L = ['Hello', 'World', 'IBM', 'Apple']

>>> [s.lower() for s in L]

['hello', 'world', 'ibm', 'apple']

1.3.10 使用列表的一部分

你可以处理列表的部分元素，Python称之为切片。

要创建切片，可指定要使用的第一个元素和最后一个元素的索引。

>>> players = ['charles', 'martina', 'michael', 'florence', 'eli']

>>> print(players[0:3])

['charles', 'martina', 'michael']

>>> print(players[:4]) # 如果你没有指定第一个索引，Python将自动从列表开头开始

['charles', 'martina', 'michael', 'florence']

>>> print(players[2:]) # 要让切片终止于列表末尾，也可使用类似的语法

['michael', 'florence', 'eli']

>>> print(players[-3:]) # 负数索引返回离列表末尾相应距离的元素

['michael', 'florence', 'eli']

复制列表

my_foods = ['pizza', 'falafel', 'carrot cake']

friend_foods = my_foods[:] # 使用[:]来复制列表

my_foods.append('cannoli')

friend_foods.append('ice cream')

print("My favorite foods are:")

print(my_foods)

print("\nMy friend's favorite foods are:")

print(friend_foods)

# My favorite foods are:

# ['pizza', 'falafel', 'carrot cake', 'cannoli']

#

# My friend's favorite foods are:

# ['pizza', 'falafel', 'carrot cake', 'ice cream']

1.4 Tuple(元组)

Python将不能修改的值称为不可变的，而不可变的列表称为元组。

元组看起来犹如列表，但使用圆括号而不是方括号来标识。

元组中只包含一个元素时，需要在元素后面添加逗号，否则括号会被当作运算符使用。

>>> tup1 = (50)

>>> type(tup1)

>>> tup1 = (50,)

>>> type(tup1)

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