ZEMMOURA Khalil Zakaria wrote:
> Hi,
>
> I am playing with python3.6 and i noticed a change in the behaviour of the
> open() builtin function.
>
> The file opened using open() is closed automaticaly after iterationg over
> it in the python shell
>
> Here is the dummy code i am using:
>
> # Beggin
>
> testfile = open('test.txt')
> for line in testfile:
> print(line)
>
> # End
>
> the first time the code runs well and gives me the expected result.
> the secod time that i run the loop, nothing is printed on the screen.
That is not new. The file is not closed, you have just reached the end of it
>>> f = open("tmp.txt")
>>> for line in f: print(line, end="")
...
alpha
beta
gamma
>>> for line in f: print(line, end="")
...
>>>
You can move the file pointer with seek:
>>> f.seek(0)
0
>>> for line in f: print(line, end="")
...
alpha
beta
gamma
>
> when i type:
>
> testfile.close and press the tab key to autocomplete:
>
> here is what i get
>>>> testfile.close( testfile.closed
There is an attribute "closed" that tells you the state of the file and a
close() method that closes an open file and does nothing if the file is
already closed:
>>> f.close()
>>> f.closed
True
>>> f.close()
When you try to iterate over a closed file an exception is raised:
>>> for line in f: print(line, end="")
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: I/O operation on closed file.
> when i run that commande and ignore the message:
> testfile.close()
> nothing is prined on the terminal, and python runs the commande as if the
> file is still opened.
I doubt that.
> i searched in the doc and this behaviour is not documented.
The documentation is not as concise as one might wish. Have a look at
<https://docs.python.org/dev/library/io.html>.
> I don't now if it is a bug or i didn't search in the right place.
No bug.
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor
