1. 读写文件笔记（第8章）

1.1 文件与文件路径
通过import os调用os模块操作目录，常用函数如下：

1.2 文件读写

在Python 中，读写文件有3 个步骤：

1. 调用open()函数，返回一个File 对象。
2. 调用File 对象的read()或write()方法。
3. 调用File 对象的close()方法，关闭该文件

# 将'w'作为第二个参数传递给open(),以写模式打开该文件
# 写模式会清空源文件
baconFile = open('bacon.txt', 'w')
baconFile.write('Hello world!\n')
baconFile.close()

# 将'a'作为第二个参数传递给open()，以添加模式打开该文件
# 添加模式将在已有文件的末尾添加文本
baconFile = open('bacon.txt', 'a')
baconFile.write('Bacon is not a vegetable.')
baconFile.close()

# 读文件
baconFile = open('bacon.txt')
# read将文件的内容看成是单个大字符串
content = baconFile.read()
# readlines从该文件取得一个字符串的列表。列表中的每个字符串就是文本中的每一行
# content = baconFile.readlines()
baconFile.close()
print(content)

Hello world!
Bacon is not a vegetable.

2. 项目练习

2.1 生成随机的测验试卷文件

# -*- coding: utf-8 -*-
import random


# 测验数据
# The quiz data. Keys are states and values are their capitals.
capitals = {'Alabama': 'Montgomery', 'Alaska': 'Juneau', 'Arizona': 'Phoenix',
'Arkansas': 'Little Rock', 'California': 'Sacramento', 'Colorado': 'Denver',
'Connecticut': 'Hartford', 'Delaware': 'Dover', 'Florida': 'Tallahassee',
'Georgia': 'Atlanta', 'Hawaii': 'Honolulu', 'Idaho': 'Boise', 'Illinois':
'Springfield', 'Indiana': 'Indianapolis', 'Iowa': 'Des Moines', 'Kansas':
'Topeka', 'Kentucky': 'Frankfort', 'Louisiana': 'Baton Rouge', 'Maine':
'Augusta', 'Maryland': 'Annapolis', 'Massachusetts': 'Boston', 'Michigan':
'Lansing', 'Minnesota': 'Saint Paul', 'Mississippi': 'Jackson', 'Missouri':
'Jefferson City', 'Montana': 'Helena', 'Nebraska': 'Lincoln', 'Nevada':
'Carson City', 'New Hampshire': 'Concord', 'New Jersey': 'Trenton', 'New Mexico': 'Santa Fe', 'New York': 'Albany', 'North Carolina': 'Raleigh',
'North Dakota': 'Bismarck', 'Ohio': 'Columbus', 'Oklahoma': 'Oklahoma City',
'Oregon': 'Salem', 'Pennsylvania': 'Harrisburg', 'Rhode Island': 'Providence',
'South Carolina': 'Columbia', 'South Dakota': 'Pierre', 'Tennessee':
'Nashville', 'Texas': 'Austin', 'Utah': 'Salt Lake City', 'Vermont':
'Montpelier', 'Virginia': 'Richmond', 'Washington': 'Olympia', 
'West Virginia': 'Charleston', 'Wisconsin': 'Madison', 'Wyoming': 'Cheyenne'}
    
    
# 生成试卷
# 试卷份数    
n_quiz=2
for quizNum in range(n_quiz):
    # Create the quiz and answer key files.
    # 试卷
    quizFile = open('capitalsquiz%s.txt' % (quizNum + 1), 'w')
    # 答案
    answerKeyFile = open('capitalsquiz_answers%s.txt' % (quizNum + 1), 'w')
    # Write out the header for the quiz.
    # 头文件
    quizFile.write('Name:\n\nDate:\n\nPeriod:\n\n')
    quizFile.write((' ' * 20) + 'State Capitals Quiz (Form %s)' % (quizNum + 1))
    quizFile.write('\n\n')
    # Shuffle the order of the states.
    states = list(capitals.keys())
    # 创建了美国州名的随机列表
    random.shuffle(states)    
    
    
    # 创建答案    
    # Loop through all 50 states, making a question for each.
    for questionNum in range(50):
        # Get right and wrong answers.
        # 正确答案
        correctAnswer = capitals[states[questionNum]]
        # 错误答案
        wrongAnswers = list(capitals.values())
        # 删除正确的答案
        del wrongAnswers[wrongAnswers.index(correctAnswer)]
        # 随机取出三个答案
        wrongAnswers = random.sample(wrongAnswers, 3)
        answerOptions = wrongAnswers + [correctAnswer]
        random.shuffle(answerOptions)    
    
        # 将内容写入测验试卷和答案文件
        # Write the question and the answer options to the quiz file.
        quizFile.write('%s. What is the capital of %s?\n' % (questionNum + 1,states[questionNum]))
        
    
        for i in range(4):
            quizFile.write(' %s. %s\n' % ('ABCD'[i], answerOptions[i]))
        quizFile.write('\n')
        
        # Write the answer key to a file.   
        answerKeyFile.write('%s. %s\n' % (questionNum + 1, 'ABCD'[answerOptions.index(correctAnswer)]))
    quizFile.close()
    answerKeyFile.close()

2.2 疯狂填词

创建一个疯狂填词（Mad Libs）程序，它将读入文本文件，并让用户在该文本文件中出现ADJECTIVE、NOUN、ADVERB 或VERB 等单词的地方，加上他们自己的文本。

import re

# text:
'''
The ADJECTIVE panda walked to the NOUN and then VERB. A nearby NOUN was unaffected by these events
'''
# 输入文件
input_file = open('./input_text.txt')
input_text = input_file.read()
input_file.close()

# 输出文本
output_text = input_text

# 输入文本寻找关键词
keywords = re.compile('adjective|noun|verb', re.IGNORECASE)
mo = keywords.findall(input_text)

# 一个一个词进行替换
for word in mo:
    if word[0].lower() == 'a':
        replacewords = input('Enter an {}:\n'.format(word))
    else:
        replacewords = input('Enter a {}:\n'.format(word))
    regex = re.compile(word)
    # 每一次替换一个词
    output_text = regex.sub(replacewords, output_text, 1)

# 写入新文件
output_file = open('output_text.txt', 'w')
output_file.write(output_text)
output_file.close()
print(output_text)

Enter an ADJECTIVE:
silly
Enter a NOUN:
chandelier
Enter a VERB:
screamed
Enter a NOUN:
pickup truck
The silly panda walked to the chandelier and then screamed. A nearby pickup truck was unaffected by these events.

2.3 正则表达式查找

编写一个程序，打开文件夹中所有的.txt 文件，查找匹配用户提供的正则表达式的所有行。结果应该打印到屏幕上。

import os
import re

path = "./"

# 判断路径目录是否存在
folder = os.path.exists(path)
if folder == False:
    print("文件目录不存在！")


#返回指定目录下所有的文件名和文件夹名列表
file_Name = os.listdir(path)

#创建正则表达式
keywords = re.compile(r'ADJECTIVE')

# 找出txt文件
for i in range(len(file_Name)):
    #判断是否为txt文件
    if os.path.isfile(os.path.join(path, file_Name[i])) and file_Name[i].split('.')[-1] == 'txt':
        # 打开文件
        file = open(os.path.join(path, file_Name[i]))
        file_texts = file.readlines()
        for texts in file_texts:
            #找出匹配正则表达式的内容
            text_put = keywords.search(texts)
            #输出结果
            if text_put != None:
                #打印当前行
                print('{}'.format(texts))

The ADJECTIVE panda walked to the NOUN and then VERB. A nearby NOUN was unaffected by these events.