python - Python读/写文件而不关闭

Question

有时当我打开一个文件以在 Python 中读取或写入时

f = open('workfile', 'r')

或者

f = open('workfile', 'w')

我读/写文件，最后我忘了做f.close(). 有没有办法在所有读/写完成后自动关闭，或者在代码完成处理后自动关闭？

Answer 1

with open('file.txt','r') as f:
    #file is opened and accessible via f 
    pass
#file will be closed before here 

Answer 2

你总是可以使用with...as语句

with open('workfile') as f:
    """Do something with file"""

或者你也可以使用try...finally 块

f = open('workfile', 'r')
try:
    """Do something with file"""
finally:
    f.close()

虽然你说你忘记添加 f.close()，但我猜 with...as 语句对你来说是最好的，而且考虑到它的简单性，很难看出不使用它的原因！

Answer 3

Whatever you do with your file, after you read it in, this is how you should read and write it back:

$ python myscript.py sample.txt sample1.txt

Then the first argument (sample.txt) is our "oldfile" and the second argument (sample1.txt) is our "newfile". You can then do the following code into a file called "myscript.py"

    from sys import argv
    script_name,oldfile,newfile = argv
    content = open(oldfile,"r").read()
    # now, you can rearrange your content here
    t = open(newfile,"w")
    t.write(content)
    t.close()