1.从一个文件中读取内容（比如有3列内容），然后再新增加2列字段，并存放在列表中（一共5列）。

2.打开一个新的文件，循环包含有5列表字段的列表，并将内容写进新的文件。

import random

def writecChannelIdFile(fp, writeFile):
    channel_ids = {'125002805': "135379412029940069", '125102805': "287200733847731473"}  # 125002805：微信 125102805：支付宝
    channel_id = ['125002805', '125102805']
    with open(fp, "r") as ff:
        myReadFile = ff.readlines()
        orderList = []
        for line in myReadFile:
            channel_id_choice = random.choice(channel_id)  #随机取列表的内容（一定要放在for循环里面）

            newLine = line.replace("\n", ",")+channel_id_choice +"," + channel_ids[channel_id_choice]
            print(newLine)
            orderList.append(newLine)

    with open(writeFile, 'w')as wf:
        for order in orderList:
            print(order)
            wf.write(order+"\n")

if __name__ == "__main__":
    fp = r"D:\xxx\xxx\xxx\a.txt"            #读取该路径下的a.txt文件
    writeFile = r"D:\xxx\xxx\xxx\b.txt"     #会在该路径下生成一个b.txt的文件
    writecChannelIdFile(fp, writeFile)