Vfrdtyky

I was experimenting with opening text editors from my python script and I noticed something that apparently contradicts my understanding of the documentation of tempfile.

My experiment started out with Alex Martelli's answer.

My code -

import os

import tempfile

import subprocess



f = tempfile.NamedTemporaryFile(mode='w+t', delete=True)

n = f.name

print('Does exist? : {0}'.format(os.path.exists(n)))

f.close()

print('Does exist? : {0}'.format(os.path.exists(n)))



subprocess.run(['nano', n])

with open(n) as f:

    print (f.read())



print('Does exist? : {0}'.format(os.path.exists(n)))

OUTPUT:

Does exist? : True

Does exist? : False

Hello from temp file.



Does exist? : True

In the code, I explicitly call close on the file object declared with delete=True, however even then I am able to write and read contents to it. I don't understand why this is happening.
According to the docs-

If delete is true (the default), the file is deleted as soon as it is closed.

If calling close deletes the file then I SHOULD NOT be able to write and then read it. But it displays the correct contents of the file that you enter when nano executes. And like a tempfile, the file is not visible in the directory where I opened the terminal and ran the script.
What is even more strange is that os.path.exists works correctly for the first two times and possibly incorrectly for the third time.

Am I missing something here?

Additional Experiment:

If I run the following code then I can clearly see the file created. But that doesn't happen in the original code.

n = '.temp'

subprocess.run(['nano', n])

with open(n) as f:

    print (f.read())



print('Does exist? : {0}'.format(os.path.exists(n)))

Lets have a deeper look at your code.

First you create your temp file

f = tempfile.NamedTemporaryFile(mode='w+t', delete=True)

n = f.name

print('Does exist? : {0}'.format(os.path.exists(n)))

and this output

Does exist? : True

so there is nothing to worry about. Then in the next statements

f.close()

print('Does exist? : {0}'.format(os.path.exists(n)))

you are closing the file and actually the file gets deleted, because you are getting the following output:

Does exist? : False

Afterwards however you are recreating your file via

subprocess.run(['nano', n])

with open(n) as f:

    print (f.read())

so this is why afterwards the command

print('Does exist? : {0}'.format(os.path.exists(n)))

returns

Does exist? : True