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')