Python 修改文件指定行内容的教程

def getBooks(file):     """     该函数 `getBooks` 读取一个文件，将其内容分割成行，然后将每一行分割成     键值对，创建一个表示图书的字典列表。      :param file: `file` 参数是包含图书信息的文件名或路径     :return: 字典列表，其中每个字典表示一本书，包含其属性的键值对。     """     # 打开文件     with open(file, 'r') as booksFile:         content = booksFile.read().splitlines()      # 将每一行分割成列表     lines=[line.split(' -- ') for line in content]      # 将每一行中的条目转换为字典的键值对     books=[dict(entry.split(':') for entry in line) for line in lines]      return books

def decrementBookUnits(books,isbn):     """     `decrementBookUnits` 函数接收一个图书列表和一个 ISBN 号码，并将具有给定     ISBN 号码的图书的 ISBN 更新为 '666'。      :param books: 一个表示图书的字典列表。每个字典包含关于     图书的信息，包括其 ISBN。     :param isbn: `isbn` 参数是要减少单位的图书的 ISBN（国际标准书号）。     :return: 更新后的图书列表，在减少了具有给定 ISBN 的图书的单位后。     """     # 遍历图书列表     for idx, entry in enumerate(books):         # 检查此条目是否具有我们的 ISBN         if entry['ISBN'] == str(isbn):             # 通过直接更新实际的 `books` 对象，更新图书条目的 ISBN             books[idx]['ISBN'] = '666'              # 或者实际减少：             # books[idx]['ISBN'] = str(int(books[idx]['ISBN']) - 1)     return books

def writeBooks(books, file):     """     `writeBooks` 函数接收一个图书列表和一个文件名作为输入，打开文件，遍历     图书，并将每个图书条目以特定格式写入文件。      :param books: "books" 参数是一个字典列表。每个字典表示一本书，并且     包含该书的不同属性的键值对，例如标题、作者、类型等。     :param file: `file` 参数是图书将被写入的文件名或路径。     """     # 打开文件，遍历条目，并写回     with open(file, 'w') as booksFile:         for entry in books:             booksFile.writelines(' -- '.join(['='.join([k,v]) for k,v in entry.items()]) + 'n')

def getBooks(file):     """     The function `getBooks` reads a file, splits its content into lines, and then splits each line into     key-value pairs to create a list of dictionaries representing books.      :param file: The `file` parameter is the name or path of the file that contains the book information     :return: a list of dictionaries, where each dictionary represents a book with key-value pairs for     its attributes.     """     #open the file     with open(file, 'r') as booksFile:         content = booksFile.read().splitlines()      #split each line to a list     lines=[line.split(' -- ') for line in content]      #turn entries in each line into a key:val pair for a dictionary     books=[dict(entry.split(':') for entry in line) for line in lines]      return books  def decrementBookUnits(books,isbn):     """     The function `decrementBookUnits` takes a list of books and an ISBN number, and updates the ISBN of     the book with the given ISBN number to '666'.      :param books: A list of dictionaries representing books. Each dictionary contains information about     a book, including its ISBN     :param isbn: The `isbn` parameter is the ISBN (International Standard Book Number) of the book that     you want to decrement the units for     :return: the updated list of books after decrementing the units of a book with the given ISBN.     """     #iterate through the books list     for idx, entry in enumerate(books):         #check if this entry has our isbn         if entry['ISBN'] == str(isbn):             #update the books entry's ISBN by updating the             # actual `books` object directly using the idx             books[idx]['ISBN'] = '666'              #or actually decrement:             #books[idx]['ISBN'] = str(int(books[idx]['ISBN']) - 1)     return books  def writeBooks(books, file):     """     The function `writeBooks` takes a list of books and a file name as input, opens the file, iterates     through the books, and writes each book entry to the file in a specific format.      :param books: The "books" parameter is a list of dictionaries. Each dictionary represents a book and     contains key-value pairs for different attributes of the book, such as title, author, genre, etc     :param file: The `file` parameter is the name or path of the file where the books will be written     """     #Open file, iterate entries, and write back out     with open(file, 'w') as booksFile:         for entry in books:             booksFile.writelines(' -- '.join(['='.join([k,v]) for k,v in entry.items()]) + 'n')  #get the contents of the book an object # defined by the function books=getBooks('books.txt')  #see what this looks like print(books)  #decrement books with an ISBN of 33 books=decrementBookUnits(books,33)  #write our books object back out to a file # using a new file so this can be run over # and over again. writeBooks(books,'books2.txt')