Python - 读取、写入和附加到文件答案

【问题标题】：Python - read, write and append to a filePython - 读取、写入和附加到文件
【发布时间】：2013-11-29 01:14:31
【问题描述】：

我是 python 新手。在一个文件中有不同的端口号。我想遍历端口号。端口用逗号分隔。最后，我想在该文件中附加我的端口号。我写的代码不起作用，因为最后总是有一个换行符。我怎么解决这个问题。并且有没有更好的解决方案。这是我的代码 -

        f = open("ports.txt", "r")
        line = f.readline()
        line = line.split(",")
        print(line)

        if len(line) > 0:
            del line[-1]
        for port in line:
            print(port)
        f = open("ports.txt", "a")
        m = str(self.myPort)+","
        f.write(m)
        f.close()

【问题讨论】：

标签： python file file-io python-3.x

【解决方案1】：

# read port-list
with open('ports.txt') as inf:
    ports = [int(i) for line in inf for i in line.split(',')]

# display ports
for port in ports:
    print(port)

# recreate file
ports.append(myPort)
ports.sort()
with open('ports.txt', 'w') as outf:
    outf.write(','.join(str(p) for p in ports))

【讨论】：

感谢您的慷慨评论。很抱歉问这个问题，但是“ ports = [int(i) for line in inf for i in line.split(',')] ”是什么意思？
@eddard.stark：对于 ports.txt 文件中的每一行，它会拆分逗号分隔的数字并将每个数字转换为整数。然后它将所有这些都返回到一个列表中。
最好使用csv模块的方法来提取值，而不是重新发明轮子

【解决方案2】：

在处理逗号分隔值时，通常应使用csv module。

下面的代码应该是不言自明的。

import csv

# By using the with statement, you don't have to worry about closing the file
# for reading/writing. This is taken care of automaticly.
with open('ports.txt') as in_file:
    # Create a csv reader object from the file object. This will yield the
    # next row every time you call next(reader)
    reader = csv.reader(in_file)

    # Put the next(reader) statement inside a try ... except block. If the
    # exception StopIteratorion is raised, there is no data in the file, and
    # an IOError is raised.
    try:
        # Use list comprehension to convert all strings to integers. This 
        # will make sure no leading/trailing whitespace or any newline 
        # character is printed to the file
        ports = [int(port) for port in next(reader)]
    except StopIteration:
        raise IOError('No data in file!')

with open('ports.txt', 'wb') as out_file:
    # Create a csv writer object
    writer = csv.writer(out_file)
    # Append your port to the list of ports...
    ports.append(self.myPort)
    # ...and write the data to the csv file
    writer.writerow(ports)

【讨论】：