Python序列——列表

1. 列表是什么

列表也是序列的一种。列表能保存任意数目的Python对象，列表是可变类型。

1.1 创建列表

列表可以使用[]来创建，或者使用工厂方法list()来创建。

>>> t = list()

>>> type(t)

<type 'list'>

>>> l = []

>>> type(l)

<type 'list'>

>>> t == l

True

1.2 访问列表和更新列表

>>> t = list('furzoom')

>>> t

['f', 'u', 'r', 'z', 'o', 'o', 'm']

>>> t[1]

'u'

>>> t[2] = 'n'

>>> t

['f', 'u', 'n', 'z', 'o', 'o', 'm']

>>> t.append('.')

>>> t

['f', 'u', 'n', 'z', 'o', 'o', 'm', '.']

>>> del t[3]

>>> t

['f', 'u', 'n', 'o', 'o', 'm', '.']

>>> del t

>>> t

Traceback (most recent call last):

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

NameError: name 't' is not defined

2. 列表相关操作

支持比较运算、切片[]或者[:]、in, not in、连接操作符+、重复操作。

如果可以，尽量使用list.extend()方式代替连接操作符。

列表还支持非常重要的列表解析操作。

>>> [i for i in xrange(10)]

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

3. 内建函数对列表的支持

3.1 cmp()

比较原则：

对两个列表的元素进行比较。
如果比较的元素是同类型的，则比较其值，返回结果。
如果两个元素不是同一类型的，则检查它们是否是数字。

3.1 如果是数字，执行必要的数字强制类型转换，然后比较。

3.2 如果有一方的元素是数字，则另一方的元素大。

3.3 否则，通过类型名字的字母顺序进行比较。
如果有一个列表首先到达末尾，则另一个长一点的列表大。
如果两个列表都到达结尾，且所有元素都相等，则返回0。

3.2 序列类型函数

len()
max()
min()
sorted()
reversed()
enumerate()
zip()
sum()
list()
tuple()

4. 列表内建函数

list.append(x)
list.extend(x)
list.count(x)
list.index(x[, start[, end]])
list.insert(index, x)
list.pop([index])
list.remove(x)
list.remove()
list.sort([cmp[, key[, reverse]]])

5. 列表应用

5.1 堆栈

#!/usr/bin/env python

# -*- coding: utf-8 -*-

stack = []

def pushit():

    stack.append(raw_input('Enter New string: ').strip())

def popit():

    if len(stack) == 0:

        print 'Cannot pop from an empty stack!'

    else:

        print 'Removed [', `stack.pop()`, ']'

def viewstack():

    print stack

CMDs = {'u': pushit, 'o': popit, 'v': viewstack}

def showmenu():

    pr = """

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: """

    while True:

        while True:

            try:

                choice = raw_input(pr).strip()[0].lower()

            except (EOFError, KeyboardInterrupt, IndexError):

                choice = 'q'

            print '\nYou picked: [%s]' % choice

            if choice not in 'uovq':

                print 'Invalid option, try again'

            else:

                break

        if choice == 'q':

            break

        CMDs[choice]()

if __name__ == '__main__':

    showmenu()

运行示例如下：



    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: u

You picked: [u]

Enter New string: Python

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: u

You picked: [u]

Enter New string: is

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: u

You picked: [u]

Enter New string: cool!

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: v

You picked: [v]

['Python', 'is', 'cool!']

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: o

You picked: [o]

Removed [ 'cool!' ]

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: o

You picked: [o]

Removed [ 'is' ]

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: o

You picked: [o]

Removed [ 'Python' ]

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: o

You picked: [o]

Cannot pop from an empty stack!

    p(U)sh

    p(O)p

    (V)iew

    (Q)uit

    Enter choice: ^D

You picked: [q]

5.2 队列

#!/usr/bin/env python

# -*- coding: utf-8 -*-

queue = []

def enQ():

    queue.append(raw_input('Enter New string: ').strip())

def deQ():

    if len(queue) == 0:

        print 'Cannot pop from an empty queue!'

    else:

        print 'Removed [', `queue.pop(0)`, ']'

def viewQ():

    print queue

CMDs = {'e': enQ, 'd': deQ, 'v': viewQ}

def showmenu():

    pr = """

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: """

    while True:

        while True:

            try:

                choice = raw_input(pr).strip()[0].lower()

            except (EOFError, KeyboardInterrupt, IndexError):

                choice = 'q'

            print '\nYou picked: [%s]' % choice

            if choice not in 'edvq':

                print 'Invalid option, try again'

            else:

                break

        if choice == 'q':

            break

        CMDs[choice]()

if __name__ == '__main__':

    showmenu()

运行示例如下：



    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: e

You picked: [e]

Enter New string: Bring out

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: e

You picked: [e]

Enter New string: your dead!

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: v

You picked: [v]

['Bring out', 'your dead!']

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: d

You picked: [d]

Removed [ 'Bring out' ]

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: d

You picked: [d]

Removed [ 'your dead!' ]

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: d

You picked: [d]

Cannot pop from an empty queue!

    (E)nqueue

    (D)equeue

    (V)iew

    (Q)uit

    Enter choice: ^D

You picked: [q]