CSV错误打开文件

Question

我收到一个错误，打开一个我无法解析的文件。我能够使用我编写的另一个小程序打开 这个确切的文件，没有任何问题。

的第一个程序（不起作用）：

import csv 


passwd = "f:\mark\python\etc_password.txt" 
output = "f:\mark\python\output.txt" 

with open(passwd, 'r') as passwd1, open(output, 'w') as output1: 
    ro = csv.reader(passwd1, delimiter=':') 
    wo = csv.writer(output1, delimiter='\t') 

for record in ro: 
    # if not record[0].startswith('#'): 
    if len(record) > 1: 
     wo.writerow((record[0], record[2])) 

---

错误：

Traceback (most recent call last): 
    File "C:/Users/Mark/PycharmProjects/main/main.py", line 11, in <module> 
    for record in ro: 
ValueError: I/O operation on closed file. 

---

第二个程序（工作）：

etcfile = "f:\mark\python\etc_password.txt" 
users = {} 
with open(etcfile, "r") as datafile: 
    for line in datafile: 
     if not line.startswith("#"): 
      info = line.split(':') 
      users[info[0]] = info[2] 

for username in sorted(users): 
    print("{}:{}".format(username, users[username])) 

第一个程序存在我无法弄清楚的问题。第二个程序可以很好地打开同一个文件。

Answer 1

错误ValueError: I/O operation on closed file.告诉你 你无法从封闭文件中读取。如果您查看 第一个程序的缩进，您将打开一个csv阅读器，然后在with块的末尾关闭 。这种行为的一个更简单的例子是

In [1]: import csv 

In [2]: file = open('test.csv') 

In [3]: ro = csv.reader(file) 

In [4]: file.close() 

In [5]: for record in ro: 
    ...:  print(record) 
    ...:  
--------------------------------------------------------------------------- 
ValueError        Traceback (most recent call last) 
<ipython-input-5-1f7adaf76d31> in <module>() 
----> 1 for record in ro: 
     2  print(record) 
     3 

ValueError: I/O operation on closed file.