File closing

Note

In real life, the most common way to close files is use of with statement. It’s much more convenient way than to close file explicitly. But since you can also find close method in life, this section discusses how to use it.

After you finish working with file you have to close it. In some cases Python can close file itself. But it’s best not to count on it and close file explicitly.

close

Method close() met in File writing section. It was there to make sure that the content of file was written on disk.

For this, Python has a separate flush method. But since in example with file writing there was no need to perform any more operations, file could be closed.

Open the r1.txt file:

In [1]: f = open('r1.txt', 'r')

You can now read the content:

In [2]: print(f.read())
!
service timestamps debug datetime msec localtime show-timezone year
service timestamps log datetime msec localtime show-timezone year
service password-encryption
service sequence-numbers
!
no ip domain lookup
!
ip ssh version 2
!

The file object has a special closed attribute that lets you check whether a file is closed or not. If file is open, it returns False:

In [3]: f.closed
Out[3]: False

Now close file and check closed again:

In [4]: f.close()

In [5]: f.closed
Out[5]: True

If you try to read file an exception will be raised:

In [6]: print(f.read())
------------------------------------------------------------------
ValueError                       Traceback (most recent call last)
<ipython-input-53-2c962247edc5> in <module>()
----> 1 print(f.read())

ValueError: I/O operation on closed file