python核心编程第二版第9章习题答案.docx

9–1. 文件过滤. 显示一个文件的所有行, 忽略以井号( # )开头的行. 这个字符被用做Python , Perl, Tcl, 等大多脚本文件的注释符号.附加题: 处理不是第一个字符开头的注释.答案：f = open(test1.txt,r)for eachline in f:if eachline[0] == #:continueelif # in eachline:loc = eachline.find(#)print eachline[:loc]else:print eachline,9–2. 文件访问. 提示输入数字 N 和文件 F, 然后显示文件 F 的前 N 行.答案：N = int(raw_input(Enter a number: ))f = raw_input(Enter filename :)f1 = open(f,r)allline = f1.readlines()f1.close()for i in range(N):print allline[i],9–3. 文件信息. 提示输入一个文件名, 然后显示这个文本文件的总行数.答案：f = raw_input(Enter filename :)f1 = open(f,r)sum = 0for i in f1:sum += 1print sumf = raw_input(Enter filename :)f1 = open(f,r)sum = 0for i in f1:sum += 1print sum方法二:f = raw_input(Enter filename :)f1 = open(f,r)allline = f1.readlines()f1.close()print len(allline)9–4. 文件访问. 写一个逐页显示文本文件的程序. 提示输入一个文件名, 每次显示文本文件的 25 行, 暂停并向用户提示按任意键继续., 按键后继续执行.答案：f = raw_input(Enter filename :)f1 = open(f,r)allline = f1.readlines()f1.close()sum = 0for i in allline:print i,sum += 1if sum == 25:a = raw_input(press any key to continue:)sum = 0方法二import os F=raw_input(pls input a file name:) n=0 f=open(F,r) for i in f: print i, n+=1 if n==25: n=0 os.system(pause) f.close() 9-5 考试成绩，改进你的考试成绩问题（练习5-3和6-4），要求能从多个文件中读入考试成绩。文件的数据格式由你自己决定。答案：f = open(test1.txt,r)scores = []for i in f:if 0 = int(i.strip())= 100:scores.append(int(i.strip()))else:print score wrong ,please againif int(i.strip()) 60:print score is E,ielif int(i.strip()) 70:print score is D,ielif int(i.strip()) 80:print score is C,ielif int(i.strip()) 90:print score is B,ielse:print score is A,if.close()print average score is %.2f % (sum(scores)/len(scores))9–6. 文件比较. 写一个比较两个文本文件的程序. 如果不同, 给出第一个不同处的行号和列号.答案：f1 = raw_input(Enter a filename: )f2 = raw_input(Enter a filename: )F1 = open(f1,r)F2 = open(f2,r)F1allline = F1.readlines()F2allline = F2.readlines()F1.close()F2.close()len1 = len(F1allline)len2 = len(F2allline)minlen1 = min(len1,len2)for i in range(minlen1):print F1allline[i], F2allline[i]if F1allline[i] != F2allline[i]:minlen2 = min(l