字典实例：统计词频

import turtle##全局变量###词频排列显示个数count = 10#单词频率数组-作为y轴数据data = []#单词数组-作为x轴数据words = []#y轴显示放大倍数-可以根据词频数量进行调节yScale = 6#x轴显示放大倍数-可以根据count数量进行调节xScale = 30################# Turtle Start  ####################  #从点(x1,y1)到(x2,y2)绘制线段def drawLine(t, x1, y1, x2, y2):    t.penup()    t.goto (x1, y1)    t.pendown()    t.goto (x2, y2)# 在坐标(x,y)处写文字def drawText(t, x, y, text):    t.penup()    t.goto (x, y)    t.pendown()    t.write(text)def drawGraph(t):    #绘制x/y轴线    drawLine (t, 0, 0, 360, 0)    drawLine (t, 0, 300, 0, 0)    #x轴: 坐标及描述    for x in range(count):        x=x+1 #向右移一位,为了不画在原点上        drawText(t, x*xScale-4, -20, (words[x-1]))        drawText(t, x*xScale-4, data[x-1]*yScale+10, data[x-1])    drawBar(t)#绘制一个柱体def drawRectangle(t, x, y):    x = x*xScale    y = y*yScale#放大倍数显示    drawLine(t, x-5, 0, x-5, y)    drawLine(t, x-5, y, x+5, y)    drawLine(t, x+5, y, x+5, 0)    drawLine(t, x+5, 0, x-5, 0)#绘制多个柱体def drawBar(t):    for i in range(count):        drawRectangle(t, i+1, data[i])    ################# Turtle End  #####################对文本的每一行计算词频的函数def processLine(line, wordCounts):    #用空格替换标点符号    line = replacePunctuations(line)    #从每一行获取每个词    words = line.split()     for word in words:        if word in wordCounts:            wordCounts[word] += 1        else:            wordCounts[word] = 1#空格替换标点的函数def replacePunctuations(line):    for ch in line:        if ch in "~@#$%^&*()_-+=<>?/,.:;{}[]|\'""":            line = line.replace(ch, " ")    return linedef main():    #用户输入一个文件名    filename = input("enter a filename:").strip()    infile = open(filename, "r")    #建立用于计算词频的空字典    wordCounts = {}    for line in infile:        processLine(line.lower(), wordCounts)    #从字典中获取数据对    pairs = list(wordCounts.items())    #列表中的数据对交换位置,数据对排序    items = [[x,y]for (y,x)in pairs]     items.sort()     #输出count个数词频结果    for i in range(len(items)-1, len(items)-count-1, -1):        print(items[i][1]+"\t"+str(items[i][0]))        data.append(items[i][0])        words.append(items[i][1])    infile.close()    #根据词频结果绘制柱状图    turtle.title('词频结果柱状图')    turtle.setup(900, 750, 0, 0)    t = turtle.Turtle()    t.hideturtle()    t.width(3)    drawGraph(t)#调用main()函数main()

列表中数据对交换位置：
示例如下：

>>>passwd={"China":"BigCountry","Korean":"SmallCountry","France":"MediumCountry"}>>> pairs=list(passwd.items())>>>items = [[x,y] for (y,x) in pairs]>>>print(items)

运行结果：

[['BigCountry', 'China'], ['SmallCountry', 'Korean'], ['MediumCountry', 'France']]