Pyhton数据结构列表在线学习

在Python中，列表（Lists）是很常见的数据结构。今天我们要来在线学习列表的相关知识点，主要内容有列表常用操作方法、堆栈、队列、列表推导、列表内置推导以及del表达式。一起来看看吧~

1、列表常用操作方法

list.append(x)

list末尾追加元素 x，等价于 a[len(a):]=[x]

list.extend(iterable)

list末尾追加可迭代类型元素（如添加[1,2])等价于 a[len(a):]=iterable

list.insert(i,x)

list指定位置i添加元素x

list.remove(x)

list中删除元素

list.pop([i])

从指定位置[i]处删除元素,未指定位置时，默认从末尾元素删除。

list.clear()

清空list数据

list.index(x[,start[,end]])

返回x在list中首次出现的位置,start，end 指定查找的范围。

list.count(x)

返回x在list中的个数

list.sort(key=None,reverse=False)

对list进行排序

list.reverse()

list元素倒序

list.copy()

返回list的复制数据，等价于a[:]

>>> fruits = ['orange','apple','pear','banana','kiwi','apple','banana']

>>> fruits.count('apple')

2

>>> fruits.count('tangerine')

0

>>> fruits.index('banana')

3

>>> fruits.index('banana',4) # Find next banana starting a position 4

6

>>> fruits.reverse()

>>> fruits

['banana','apple','kiwi','banana','pear','apple','orange']

>>> fruits.append('grape')

>>> fruits

['banana','apple','kiwi','banana','pear','apple','orange','grape']

>>> fruits.sort()

>>> fruits

['apple','apple','banana','banana','grape','kiwi','orange','pear']

>>> fruits.pop()

'pear'

2、列表作为堆栈

堆栈的原则是数据 先进后出

>>> stack = [3,4,5]

>>> stack.append(6)

>>> stack.append(7)

>>> stack

[3,4,5,6,7]

>>> stack.pop()

7

>>> stack

[3,4,5,6]

>>> stack.pop()

6

>>> stack.pop()

5

>>> stack

[3,4]

3、列表作为队列

队列的原则是数据 先进先出

>>> from collections import deque

>>> queue = deque(["Eric","John","Michael"])

>>> queue.append("Terry") # Terry arrives

>>> queue.append("Graham") # Graham arrives

>>> queue.popleft() # The first to arrive now leaves

'Eric'

>>> queue.popleft() # The second to arrive now leaves

'John'

>>> queue # Remaining queue in order of arrival

deque(['Michael','Terry','Graham'])

4、列表推导

根据List提供的相关方法，我们可以自己根据需求创建list

>>> squares = []

>>> for x in range(10):

... squares.append(x**2)

...

>>> squares

[0,1,4,9,16,25,36,49,64,81]

也可以使用lambda表达式来创建

squares = list(map(lambda x: x**2,range(10)))

或者更直接

squares = [x**2 for x in range(10)]

使用多个for循环或者if 组合语句也可以创建list

>>> [(x,y) for x in [1,2,3] for y in [3,1,4] if x != y][(1,3),(1,4),(2,3),(2,1),(2,4),(3,1),(3,4)]

等价于

>>> combs = []

>>> for x in [1,2,3]:

... for y in [3,1,4]:

... if x != y:

... combs.append((x,y))

...

>>> combs

[(1,3),(1,4),(2,3),(2,1),(2,4),(3,1),(3,4)]

如果表达式为元组类型，使用时必须用 ()

>>> vec = [-4,-2,0,2,4]

>>> # create a new list with the values doubled

>>> [x*2 for x in vec]

[-8,-4,0,4,8]

>>> # filter the list to exclude negative numbers

>>> [x for x in vec if x >= 0]

[0,2,4]

>>> # apply a function to all the elements

>>> [abs(x) for x in vec]

[4,2,0,2,4]

>>> # call a method on each element

>>> freshfruit = [' banana',' loganberry ','passion fruit ']

>>> [weapon.strip() for weapon in freshfruit]

['banana','loganberry','passion fruit']

>>> # create a list of 2-tuples like (number,square)

>>> [(x,x**2) for x in range(6)]

[(0,0),(1,1),(2,4),(3,9),(4,16),(5,25)]

>>> # the tuple must be parenthesized,otherwise an error is raised

>>> [x,x**2 for x in range(6)]

File "<stdin>",line 1,in <module>

[x,x**2 for x in range(6)]

^

SyntaxError: invalid syntax

>>> # flatten a list using a listcomp with two 'for'

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

>>> [num for elem in vec for num in elem]

[1,2,3,4,5,6,7,8,9]

lists推导也可以用混合表达式和内置函数

>>> from math import pi

>>> [str(round(pi,i)) for i in range(1,6)]

['3.1','3.14','3.142','3.1416','3.14159']

5、列表内置推导

下面是一个 3* 4的矩阵

>>> matrix = [

... [1,2,3,4],

... [5,6,7,8],

... [9,10,11,12],

... ]

下面方法可以将matrix数据转换为 4*3的矩阵。

>>> [[row[i] for row in matrix] for i in range(4)]

[[1,5,9],[2,6,10],[3,7,11],[4,8,12]]

等价于

>>> transposed = []

>>> for i in range(4):

... transposed.append([row[i] for row in matrix])

...

>>> transposed

[[1,5,9],[2,6,10],[3,7,11],[4,8,12]]

或者是这样

>>> transposed = []

>>> for i in range(4):

... # the following 3 lines implement the nested listcomp

... transposed_row = []

... for row in matrix:

... transposed_row.append(row[i])

... transposed.append(transposed_row)

...

>>> transposed

[[1,5,9],[2,6,10],[3,7,11],[4,8,12]]

上面操作完全可以使用list的内置函数 zip() 来实现

>>> list(zip(*matrix))

[(1,5,9),(2,6,10),(3,7,11),(4,8,12)]

6、del表达式

使用可以直接删除List中的某个数值

>>> a = [-1,1,66.25,333,333,1234.5]

>>> del a[0]

>>> a

[1,66.25,333,333,1234.5]

>>> del a[2:4]

>>> a

[1,66.25,1234.5]

>>> del a[:]

>>> a

[]

也可以删除整个 list

>>> del a

Pyhton数据结构列表的学习内容就分享到这里了，相信大家对于Pyhton还有很多的疑惑，现在就在教育培训网报名在线学习Python，就有名师一对一对你进行辅导。还等什么，现在就来体验吧~