python - 在 python 中与 open() 一起使用后，打开的文件如何无法通过eek(0)倒回

Question

当我尝试在 python 中逐行打印文件内容时，如果文件是由 < 打开的，则无法通过 f.seek(0) 倒回打开的文件来打印内容强>打开(“文件名”)作为f: 但是，如果我使用 open("file_name") as f: ，我就可以做到这一点然后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Python初学者，有人能告诉我为什么吗？

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())

将在 block 末尾关闭文件(一旦文件被打印出来)

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)