Where Does Python Tempfile Writes Its Files

Where does python tempfile writes its files?

Looking at .name on a file handle is indeed one way to see where the file exists. In the case of TemporaryFile (on *NIX systems), you'll see <fdopen>, indicating an open file handle, but no corresponding directory entry. You'll need to use NamedTemporaryFile if you'd like to preserve the link to the underlying file.

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If you wish to control where temporary files go, look at the dir parameter:

TemporaryFile uses mkstemp, which allows setting the directory with the dir parameter:

If dir is specified, the file will be created in that directory; otherwise, a default directory is used. The default directory is chosen from a platform-dependent list, but the user of the application can control the directory location by setting the TMPDIR, TEMP or TMP environment variables.

Is it possible to get the path of a tempfile in Python 3

Use tempfile.NamedTemporaryFile to create a temporary file with a name, and then use the .name attribute of the object.

Note that there are platform-specific limitations on how this name can be used. The documentation says:

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).

Python - writing and reading from a temporary file

As per the docs, the file is deleted when the TemporaryFile is closed and that happens when you exit the with clause. So... don't exit the with clause. Rewind the file and do your work in the with.

with tempfile.TemporaryFile() as tmp:
    lines = open(file1).readlines()
    tmp.writelines(lines[2:-1])
    tmp.seek(0)

    for line in tmp:
        groupId = textwrap.dedent(line.split(':')[0])
        artifactId = line.split(':')[1]
        version = line.split(':')[3]
        scope = str.strip(line.split(':')[4])
        dependencyObject = depenObj(groupId, artifactId, version, scope)
        dependencyList.append(dependencyObject)

Why am I able to write to and read a tempfile even after closing it?

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

How to select the disk location for UploadFile parameter in FastAPI?

You could use Python's tempfile module to get, as well as change, the default temporary directory. Example:

import tempfile

print("Temp directory before change:", tempfile.gettempdir())
tempfile.tempdir = "path/to/tempdir/here"
print("Temp directory after change:", tempfile.gettempdir())

Passing a temporary file created with Python's tempfile to a command line program ignoring line ending preferences

I wanted to thank everyone who tried to help. The comments helped me discover another vulnerability elsewhere in my code. The problem ended up actually not being my own, rather it was the service I was using

Tempfile not found when finishing function

TemporaryFile does not return a valid filedescriptor when asked for the name attribute. You can use NamedTemporaryFile to ask for the name.

from flask import send_file
import tempfile
import csv

@app.route('/download')
def download():
    with tempfile.NamedTemporaryFile(mode='w', newline='', dir='.', suffix='.csv') as csvfilenew:
        writer = csv.writer(csvfilenew, delimiter= ';')
        writer.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])
        csvfilenew.flush()
        csvfilenew.seek(0)
        return send_file(csvfilenew.name,
            as_attachment=True,
            attachment_filename='cleanfile.csv'
        )

Another simple workaround for small amounts of data is as follows:

from flask import send_file
import csv
import io

@app.route('/download')
def download():
    with io.StringIO() as doc:
        writer = csv.writer(doc, delimiter= ';')
        writer.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])
        doc.seek(0)
        return send_file(io.BytesIO(doc.read().encode('utf8')),
            as_attachment=True,
            attachment_filename='cleanfile.csv'
        )

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