Question

当我尝试在python中逐行打印文件内容时，我无法通过 f.seek（0）来回放打开的文件，以便在文件被<打开时打印内容strong> with open（“file_name”）为f：但是，如果我使用 open（“file_name”）作为f：，我可以这样做然后 f.seek（0）

以下是我的代码

with open("130.txt", "r") as f:             #f is a FILE object
    print (f.read())                        #so f has method: read(), and f.read() will contain the newline each time 

f.seek(0)                             #This will Error!
with open("130.txt", "r") as f:       #Have to open it again, and I'm aware the indentation should change  
for line in f:                    
    print (line, end="")          

f = open("130.txt", "r")
f.seek(0)
for line in f:
    print(line, end="")

f.seek(0)                           #This time OK!
for line in f:
    print(line, end="")

我是初学者，任何人都可以告诉我为什么？

Answer 1

第一个f.seek(0)会抛出错误，因为

with open("130.txt", "r") as f:
    print (f.read())

将关闭块末尾的文件（一旦打印出文件）

您需要执行以下操作：

with open("130.txt", "r") as f:
    print (f.read())

    # in with block
    f.seek(0)

Answer 2

with的目的是在块结束时清理资源，在这种情况下包括关闭文件句柄。

尽管如此，您应该可以在.seek区块中with：

with open('130.txt','r') as f:
  print (f.read())

  f.seek(0)
  for line in f:
    print (line,end='')

在你的评论中，with在这种情况下是类似这样的语法糖：

f = open(...)
try:
  # use f
finally:
  f.close()

# f is still in scope, but the file handle it references has been closed

在python中使用open（）之后，如何通过seek（0）无法倒回打开的文件

2 个答案: