# -*- coding: utf-8 -*-
#打开文件，将文件读入字符串
col=''
f=open('pride.txt')
text=f.read()
cols=text.split()
f2=open('data.txt','w')
for col in cols:
    f2.write(col)
    f2.write('\n')

以上代码运行无误。

# -*- coding: utf-8 -*-
#打开文件，将文件读入字符串
col=''
f=open('pride.txt')
text=f.read()
cols=text.split().sort()
f2=open('data.txt','w')
for col in cols:
    f2.write(col)
    f2.write('\n')

对list进行排序后，进行写入，就出现了TypeError问题，虚心求解。

C:\Users\zhangning\Desktop\Python\learningPython\cases>python      stringTest.py
Traceback (most recent call last):
  File "stringTest.py", line 8, in <module>
    for col in cols:
TypeError: 'NoneType' object is not iterable