Python文件读写 - 读一个文件所有行，加工后写另一个文件

 #Filename: file_read_and_write.py
 #打开文件，cNames读取所有行，储存在列表中，循环对每一行在起始处加上序号1，2，3，4
 with open(r'file/companies.txt') as f1:
     cNames = f1.readlines()
     for i in range(0,len(cNames)):
         cNames[i] = str(i+1) + '.' + '' + cNames[i]

 #将处理过的cNames写入新的文件中
 with open(r'file/scompanies.txt','w') as f2:
     f2.writelines(cNames)

输入: companies.txt

google
tencent
alibaba
baidu

输出：scompanies.txt

1.google
2.tencent
3.alibaba
4.baidu