《Python核心编程》答案 第9章

Posted 2020-07-03

9-1:

filename = raw_input()
f = open(filename)
for eachLine in f:
    if eachLine[0] == ‘#‘:
        continue
    print eachLine,
f.close()

附加题：

filename = raw_input()
f = open(filename)
for eachLine in f:
    if ‘#‘ not in eachLine:
        print eachLine,
    elif eachLine[0] == ‘#‘:
        continue
    else:
        ans = ""
        for i in eachLine:
            if i == ‘#‘:
                break
            ans += i
        print ans
f.close()

9-2：

print ‘Please input number N and file F, we will display first N lines for your file‘
n = int(raw_input(‘N: ‘))
fname = raw_input(‘F: ‘)
f = open(fname)
for eachLine in f:
    if n == 0:
        break
    print eachLine,
    n -= 1
f.close()

9-3：

print ‘Enter a filename, we will display the number of lines of this file.‘
fname = raw_input()
f = open(fname)
count = 0
for eachLine in f:
    count += 1
print ‘This file has %d line(s).‘ % count
f.close()

9-4：

fname = raw_input(‘Enter a filename: ‘)
f = open(fname)
count = 0
for eachLine in f:
    count += 1
    print eachLine,
    if count % 25 == 0:
        raw_input(‘Press anykey to continue‘)
f.close()

9-5：

fname = raw_input()
f = open(fname)
sum_of_score = 0.0
count = 0
for eachLine in f:
    sum_of_score += float(eachLine)
    count += 1
avg_of_score = sum_of_score / count
if 90 <= avg_of_score <= 100:
    print ‘A‘
elif 80 <= avg_of_score <= 89:
    print ‘B‘
elif 70 <= avg_of_score <= 79:
    print ‘C‘
elif 60 <= avg_of_score <= 69:
    print ‘D‘
else:
    print ‘F‘

9-6：

print ‘Enter two file name to compare (suppose two file has same rows)‘
f1name = raw_input(‘file A: ‘)
f2name = raw_input(‘file B: ‘)
f1 = open(f1name)
f2 = open(f2name)
line = 0
same = True
for eachLine in f1:
    line += 1
    f2Line = f2.next()
    if eachLine == f2Line:
        continue
    else:
        same = False
        col = 0
        for i in eachLine:
            if i != f2Line[col]:
                break
            col += 1
        col += 1
        break
if same:
    print ‘Two files are the same‘
else:
    print ‘The first different occurs %d line %d column.‘ % (line, col)

9-7：

f = open(‘/etc/services‘)
print ‘%17s\t%5s\t%5s‘ % (‘name‘, ‘port‘, ‘protocol‘)
for eachLine in f:
    if eachLine[0] in (‘#‘, ‘\n‘):
        continue
    data = eachLine.split()
    name = data[0]
    port = data[1].split(‘/‘)[0]
    protocol = data[1].split(‘/‘)[1]
    print ‘%17s\t%5s\t%5s‘ % (name, port, protocol)
f.close()

9-8:

mname = raw_input(‘Enter a module name: ‘)
exec compile(‘import ‘ + mname, ‘‘, ‘single‘)
exec compile(‘a = dir(‘+mname+‘)‘, ‘‘, ‘single‘)
print "The attributes of", mname
print ‘%10s\t%10s\t%10s‘ % (‘name‘, ‘type‘, ‘value‘)
for eachAttr in a:
    exec compile(‘value = ‘ + mname + ‘.‘ + eachAttr, ‘‘, ‘single‘)
    print ‘%10s\t%10s\t%10s‘ % (eachAttr, type(eachAttr), value)

9-9：稍后更新

9-10：稍后更新

9-11：

（a）

import os

print ‘Welcome URL bookmark manager‘
hasdata = False
if os.path.exists(‘data.txt‘):
    datafile = open(‘data.txt‘, ‘r+‘)
    hasdata = True
else:
    datafile = open(‘data.txt‘, ‘w‘)

prompt = """
(A)dd
(U)pdate
(D)elete
(S)earch
(Q)uit
select one:
"""
data = []
if hasdata:
    temp = datafile.read().split(‘\n‘)
    for t in temp:
        data.append(t.split(‘ ‘))

while True:
    option = raw_input(prompt).lower()[0]

    if option == ‘a‘:
        site_name = raw_input(‘Site name: ‘)
        url_address = raw_input(‘URL address: ‘)
        description = raw_input(‘One line description(optional): ‘)
        data.append([site_name, url_address, ‘"‘+description+‘"‘])
    elif option == ‘u‘:
        site_name = raw_input(‘Enter the site name you want to update its url: ‘)
        url_address = raw_input(‘New url: ‘)
        for eachData in data:
            if eachData[0] == site_name:
                eachData[1] = url_address
                print ‘update succeed‘
                break
        else:
            print ‘no such site name‘
    elif option == ‘d‘:
        site_name = raw_input(‘Enter the site name you want to delete: ‘)
        for i in range(len(data)):
            if data[i][0] == site_name:
                del data[i]
                print ‘delete succeed‘
                break
        else:
            print ‘no such site name‘
    elif option == ‘s‘:
        keyword = raw_input(‘Enter the keyword in site name or url address: ‘)
        findit = False
        for eachData in data:
            for eachItem in eachData:
                if keyword in eachItem:
                    print ‘Site name: %s, URL address: %s, description: %s‘ % (eachData[0],eachData[1],eachData[2])
                    findit = True
                    break
            if findit:
                break
        if not findit:
            print ‘cannot find %s‘ % keyword
    elif option == ‘q‘:
        ans = []
        for eachData in data:
            ans.append(‘ ‘.join(eachData))
        ans = ‘\n‘.join(ans)
        datafile.seek(0)
        datafile.truncate()
        datafile.write(ans)
        datafile.close()
        break

（b）稍后更新

9-12：稍后更新

9-13：

（a）

命令行参数是调用某个程序时除程序名以外的其他参数。Unix操作系统中的命令通常会接受输入，执行一些功能，然后把结果作为流输出出来。命令行参数使程序员可以在启动一个程序的时候对程序行为做出选择。

（b）

from sys import argv
print "# of args", len(sys.argv)
print "args:", sys.argv

9-14：

from sys import argv
if len(argv) == 2:
    f = open(‘data.txt‘, ‘r+‘)
    for eachLine in f:
        print eachLine,
    f.seek(0)
    f.truncate()
    f.close()
else:
    n1 = argv[1]
    n2 = argv[3]
    op = argv[2]
    if op == ‘+‘:
        ans = float(n1) + float(n2)
    elif op == ‘-‘:
        ans = float(n1) - float(n2)
    elif op == ‘*‘:
        ans = float(n1) * float(n2)
    elif op == ‘/‘:
        ans = float(n1) / float(n2)
    elif op in (‘**‘, ‘^‘):
        ans = float(n1) ** float(n2)

    if ans == int(ans):
        ans = int(ans)
    print ans
    f = open(‘data.txt‘, ‘a+‘)
    f.write(‘%s %s %s\n‘ % (n1, op, n2))
    f.write(str(ans) + ‘\n‘)
    f.close()

9-15：

print ‘Input 2 file name, we will copy content from file1 to file2: ‘
f1name = raw_input(‘File 1: ‘)
f2name = raw_input(‘File 2: ‘)
f1 = open(f1name)
f2 = open(f2name, ‘w‘)
f2.write(f1.read())

9-16：

fname = raw_input(‘Enter file name: ‘)
f = open(fname, ‘r+‘)
content = f.readlines()
index = 0
while True:
    if (len(content[index]) > 80) and (index < len(content)-1):
        content[index+1] = content[index][80:].strip() + content[index+1].strip() + ‘\n‘
        content[index] = content[index][:80] + ‘\n‘
    elif (len(content[index]) > 80) and (index >= len(content)-1):
        content.append(content[index][80:])
        content[index] = content[index][:80] + ‘\n‘
    index += 1
    if index >= len(content):
        break

f.seek(0)
f.truncate()
f.write(‘‘.join(content))
f.close()

9-17：

print ‘Welcome to crude and elementary text file editor‘
prompt = """
(C)reate file
(D)isplay file
(E)dit file
(S)ave file
(Q)uit

select one:
"""
option = raw_input(prompt).lower()[0]
content = []
while True:
    if option == ‘c‘:
        filename = raw_input(‘Enter the file name: ‘)
        print ‘Please enter file content, end with ctrl+c‘
        try:
            while True:
                content.append(raw_input(‘->‘))
        except KeyboardInterrupt:
            print ‘create succeed!‘
    elif option == ‘d‘:
        for eachLine in content:
            print eachLine
    elif option == ‘e‘:
        line = int(raw_input(‘Which line you want to edit? ‘))
        print ‘The new content:‘
        ncontent = raw_input(‘->‘)
        content[line-1] = ncontent
    elif option == ‘s‘:
        f = open(filename, ‘w‘)
        f.write(‘\n‘.join(content))
        f.close()
    elif option == ‘q‘:
        break
    else:
        print ‘error option‘
    option = raw_input(prompt).lower()[0]

9-18：

print ‘Enter a byte value(0-255) and a filename‘
print ‘We will display the number of times that byte appers in the file.‘
value = int(raw_input(‘Byte value(0-255): ‘))
fname = raw_input(‘Filename: ‘)
f = open(fname)
ch = chr(value)
count = 0
for each in f.read():
    if each == ch:
        count += 1
print "The byte value %d(‘%s‘) appears %d times in this file."% (value, ch, count)
f.close()

9-19：

from random import randint

def mybin(n):
    ans = ‘‘
    while n != 0:
        ans = str(n % 2) + ans
        n = n / 2
    for i in range(8-len(ans)):
        ans = ‘0‘ + ans
    return int(ans)

byte_value = int(raw_input(‘Byte value: ‘))
times = int(raw_input(‘Times: ‘))
total_byte = int(raw_input(‘Total byte: ‘))

ans = []
for i in range(total_byte - times):
    num = byte_value
    while num == byte_value:
        num = randint(0,255)
    num = mybin(num)
    ans.append(str(num))

byte_value = mybin(byte_value)

for i in range(times):
    position = randint(0, total_byte - times)
    ans.insert(position, str(byte_value))

ans = ‘ ‘.join(ans)
f = open(‘data.txt‘, ‘w‘)
f.write(ans)
f.close()   

9-20 ～ 9-25：稍后更新