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I have this function that references the path of a file:

some_obj.file_name(FILE_PATH)

where FILE_PATH is a string of the path of a file, i.e. H:/path/FILE_NAME.ext

I want to create a file FILE_NAME.ext inside my python script with the content of a string:

some_string = 'this is some content'

How to go about this? The Python script will be placed inside a Linux box.

Martin Thoma
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SuperString
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2 Answers2

243

I think you're looking for a tempfile.NamedTemporaryFile.

import tempfile
with tempfile.NamedTemporaryFile() as tmp:
    print(tmp.name)
    tmp.write(...)

But:

Whether the name can be used to open the file a second time, while the named temporary file is still open, varies across platforms (it can be so used on Unix; it cannot on Windows NT or later).

If that is a concern for you:

import os, tempfile
tmp = tempfile.NamedTemporaryFile(delete=False)
try:
    print(tmp.name)
    tmp.write(...)
finally:
    tmp.close()
    os.unlink(tmp.name)
martineau
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Minras
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    this is a good answer based on the subject of the question, which google takes note of, rather than SuperString's particular problem – Sam Watkins Mar 14 '13 at 03:19
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    and you can pass an optional `dir=path` arg to `NamedTemporaryFile` if you want to control which directory it allocates it in. – stason Feb 26 '19 at 03:06
  • do you need to do os.unlink(tmp.name)? isn't the point of using tempfile to handle cleanup? – alegria Jul 14 '21 at 13:30
  • is there any chance that tempfile will create two files with the same name simultaneously? If yes, will the first file get overridden? (consider that I have multiple users which can call the function simultaneously) – Deepam Gupta Nov 18 '21 at 12:37
101

There is a tempfile module for python, but a simple file creation also does the trick:

new_file = open("path/to/FILE_NAME.ext", "w")

Now you can write to it using the write method:

new_file.write('this is some content')

With the tempfile module this might look like this:

import tempfile

new_file, filename = tempfile.mkstemp()

print(filename)

os.write(new_file, "this is some content")
os.close(new_file)

With mkstemp you are responsible for deleting the file after you are done with it. With other arguments, you can influence the directory and name of the file.

UPDATE

As rightfully pointed out by Emmet Speer, there are security considerations when using mkstemp, as the client code is responsible for closing/cleaning up the created file. A better way to handle it is the following snippet (as taken from the link):

import os
import tempfile

fd, path = tempfile.mkstemp()
try:
    with os.fdopen(fd, 'w') as tmp:
        # do stuff with temp file
        tmp.write('stuff')
finally:
    os.remove(path)

The os.fdopen wraps the file descriptor in a Python file object, that closes automatically when the with exits. The call to os.remove deletes the file when no longer needed.

Constantinius
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    This should really be updated to provide the secure way of creating tempfiles in python. Here is some examples. https://security.openstack.org/guidelines/dg_using-temporary-files-securely.html – SudoKid Feb 05 '18 at 23:28
  • Shouldn't you also `fd.close()` in the `finally` block? Check the docs for os remove regarding removing files still in use - https://docs.python.org/3/library/os.html#os.remove – Nelson Rodrigues Sep 03 '20 at 15:26
  • @NelsonRodrigues the "with" keyword automatically closes the file aliased after executing the inner code – gannonbarnett Nov 29 '20 at 02:37
  • @ganski oh I see, I thought it just closed the `tmp` object. I tested it and it also closed `fd`. – Nelson Rodrigues Dec 02 '20 at 10:43
  • How do I select the type of file that I am creating? – C0mpl3x Jun 25 '21 at 12:05
  • Also I write to the file but when I try to print(tmp.read()) I get empty field. I changed the 'w' to 'w+' – C0mpl3x Jun 29 '21 at 09:36
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    Add `tmp.flush()` after `tmp.write()` before trying to read the temp file. – jws Aug 30 '21 at 19:04