Python 字典（dict） 操作基础

Python 字典与结构化数据

1.字典基本结构

1.1 创建存储生日的字典

birthday = {'Alice':'Ar 1','Bob':'July 7'}

1.2 查询生日的小程序

while True:    print('Enter a name(blank to quit):')    name = input()    if name == '':        break    if name in birthday:        print(birthday[name] + 'is the birthday of ' + name)    else:        print("I don't know the birthday of " + name)        print("Tell me plz")        newbday = input()        birthday[name] = newbday        print('Birthday database updated')

Enter a name(blank to quit):AliceAr 1is the birthday of AliceEnter a name(blank to quit):BobJuly 7is the birthday of BobEnter a name(blank to quit):ChenI don't know the birthday of ChenTell me plzJuly 22thBirthday database updatedEnter a name(blank to quit):ChenJuly 22this the birthday of ChenEnter a name(blank to quit):I don't know the birthday of  Tell me plzBirthday database updatedEnter a name(blank to quit):

birthday

{'Alice': 'Ar 1', 'Bob': 'July 7', 'Chen': 'July 22th'}

#字典可以修改value,那么，怎么修改keybirthday['Alice'] = 'Apr 1st'birthday['Bob'] = 'July 7th'birthday

{'Alice': 'Apr 1st', 'Bob': 'July 7th', 'Chen': 'July 22th'}

2. 字典的方法

2.1 字典的 values() , keys() ,items()

for v in birthday.values():    print (v)for v in birthday.keys():    print(v)for v in birthday.items():    print(v)

Apr 1stJuly 7thJuly 22thAliceBobChen('Alice', 'Apr 1st')('Bob', 'July 7th')('Chen', 'July 22th')

'Alice' in birthday'Apr 1st' in birthday.values()'Apr 1st' in birthday.keys()

False

2.2 get方法

有对应键，返回键对应值；没有对应键存在，返回备用值

print('I think Rachel was born on '+ birthday.get('Rachel','a rainy day'))

I think Rachel was born on a rainy day

2.3 setdafault() 方法

为键赋予默认取值，返回 键的当前值；

setdefault(‘keys’,’default’)

# 字符统计程序message = 'In the preceding example, the kernel is chosen \because it represents an expansion of polynomials and can conveniently compute \high-dimensional inner products. In this example the kernel is chosen \because of its functional form in the representation 'count = {}for char in message:    count.setdefault(char,0)    count[char] = count[char] + 1print (count)

{'I': 2, 'n': 26, ' ': 37, 't': 14, 'h': 9, 'e': 32, 'p': 9, 'r': 10, 'c': 10, 'd': 4, 'i': 16, 'g': 2, 'x': 3, 'a': 12, 'm': 6, 'l': 9, ',': 1, 'k': 2, 's': 15, 'o': 14, 'b': 2, 'u': 5, 'f': 4, 'y': 2, 'v': 1, '-': 1, '.': 1}

2.4 漂亮打印 pprint 模块

import pprintpprint.pprint(count)# 等价于 print(pprint.pformat(count))

{' ': 37, ',': 1, '-': 1, '.': 1, 'I': 2, 'a': 12, 'b': 2, 'c': 10, 'd': 4, 'e': 32, 'f': 4, 'g': 2, 'h': 9, 'i': 16, 'k': 2, 'l': 9, 'm': 6, 'n': 26, 'o': 14, 'p': 9, 'r': 10, 's': 15, 't': 14, 'u': 5, 'v': 1, 'x': 3, 'y': 2}

3.小练习

3.1 井字棋

theBoard = {'top-l':'' , 'top-m':'' , 'top-r':'',            'mid-l':'' , 'mid-m':'' , 'mid-r':'',            'low-l':'' , 'low-m':'' , 'low-r':''}def printBoard(board):    print(board['top-l'] + ' | ' + board['top-m'] + '| '+board['top-r'])    print('-+-+-')    print(board['mid-l'] + ' | ' + board['mid-m'] + '| '+board['mid-r'])    print('-+-+-')    print(board['low-l'] + ' | ' + board['low-m'] + '| '+board['low-r'])    print('-+-+-')def gameStart():    printBoard(theBoard)    i = 0    while True:        chess = ['O','X']        print('where do you wanna place')        position = input()        if theBoard[position]:            print('already full')            print('Another choice plz')            position = input()        theBoard[position] = chess[i]        printBoard(theBoard)        i = 1 - i        #判断棋盘是否已满，笨办法        k = 0        for value in theBoard.values():            if value:                k = k+1        if k >=9 :            print('All full,the end')            break

3.2 嵌套的字典和列表

• 对复杂事物进行建模，字典列表中可能包含其他字典列表；
• 列表适合包含一组有序的值，字典适合包含关联的键和值

#示例程序：统计野餐事物总数allGuests = {'Ali':{'apple':16,'bread':12},             'Bob':{'ham':1,'coffee':32,'apple':3},            'Carol':{'bread':23,'coffee':2}}def totalBrought(guests,item):    numBrought = 0    for k,v in guests.items():                   #字典中item的循环 k,v        numBrought = numBrought + v.get(item,0)    return numBroughtprint('Number of things being brought:')print('- apples :'+ str(totalBrought(allGuests,'apple')))print('- bread ：' + str(totalBrought(allGuests,'bread')))print('- coffee ：'+ str(totalBrought(allGuests,'coffee')))

Number of things being brought:- apples :19- bread ：35- coffee ：34

3.3 好玩游戏的物品清单

stuff = {'rope':5,'torch':2,'gold':100,'sword':1}def inventoryDisplay(stuff):    numTotal = 0    print('Inventory:')    for k,v in stuff.items():        print( k +':'+ str(v))        numTotal = numTotal + v    print ('total:'+ str(numTotal))#屠龙战利品 以列表形式存储dragonLoot = ['rope','rope','torch','gold','gold','gold','diamond']#列表到字典的函数def addToInventory(loot,stuff):    countLoot = {}    for k in loot:        countLoot.setdefault(k,0)        countLoot[k] = countLoot[k] + 1    for l in countLoot.keys():        stuff.setdefault(l,0)        stuff[l] = stuff[l] + countLoot[l]    return stuffinventoryDisplay(stuff)print(addToInventory(dragonLoot,stuff))

Inventory:rope:5torch:2gold:100sword:1total:108{'rope': 7, 'torch': 3, 'gold': 103, 'sword': 1, 'diamond': 1}

参考文献
《Python编程快速上手–让繁琐工作自动化》